1. On the Wagons, Off the Wagons… The Infantry Fighting Vehicle Problem
© IWM (H9234)
Thanks to the IWM for permission to use this marvellously energetic image. It shows soldiers of 2 Mons dismounting from their Universal Carrier during an exercise near Newry, Northern Ireland, 26th April 1941.
Dr John D Salt
Mounted and Dismounted Close Combat Symposium July 2015

2. What Do You Call Your Vehicle?
A tank man speaks of his panzer
A recce trooper has a car
An infanteer rides in a wagon
All images © Wikimedia Commons
“Panzer” is a name suitably redolent of Blitzkrieg.
“Car” suggests touring.
“Wagon” definitely suggest transport – a means of getting a load of passengers from A to B.
Getting off the vehicle might be called “dismounting” in the HCav and RAC, but infantry have always “debussed”. Variant terms are “disembus” (opposite of “embus”), and, while the Kangaroo was the APC in use, “de-pouch”.
The phrase “On the wagons, off the wagons” is traditionally used, like “Hurry up and wait” and “Haven’t you heard? It’s all been changed”, to indicate a state of military disorder.
Perhaps the most highly-compounded compound verb ever used was that used by an NCO presiding over a busload of national servicemen during one such bout of military confusion. Having got off the wagon at one location, discovered it was the wrong place, got back on, and driven to a second location, the men were instructed to get off the wagon again by the NCO in charge with the order to “redisembus”.

3. When Should Infantry Fight Mounted, and When Dismounted?
Rowland and Speight’s model of the rural infantry battle
Relative vulnerability of personnel and vehicles to point and area fire
Balanced and unbalanced organisations for fire and movement
Simpkin’s dismount doctrine triangle
Firing ports and close-in weapons
Achieving shock
How many kinds of infantry-carrying vehicle?
How many kinds of infantry?

4. Pattern of the Rural Infantry Battle
After L R Speight and D Rowland, Modelling The Rural Infantry Battle: Overall Structure and a Basic Representation of the Approach Battle, Military Operations Research 11(1):5-26, November 2006
Attackers may stall, or defenders
withdraw, in any phase
If attackers still advancing at 30m,
defenders probably overrun
Attacking infantry
unmask
Defending infantry
unmask
This is a very general pattern, and the distances are broad indications only. Evidently a cunning attacker may be able to use poor visibility or covered approaches to unmask at closer ranges than 300m. British doctrine has traditionally demanded fields of fire of at least 200m, with 100m being an absolute minimum.
The phase changes at 300m and 30m can be taken as approximately the distances at which the attackers cross the effective Fire Line (EFL) and enter the Final Assault Position (FAP). They also fit the long-standing and successful pattern of British infantry training, corresponding to the transitions between the advance to contact and reaction to enemy fire/winning the firefight, and fire and movement and the assault, respectively.
Before the attackers cross the EFL, both sides will take casualties from area fire only. Evidently the attacker is much more exposed, and intelligent selection of Defensive Fire (DF) tasks by sustained fire (SF) MGs, mortars and artillery, and artillery counter-preparation fire, might cause enough damage to force the attack to stall before it even reaches the EFL.
Once the attackers cross the EFL, unsuppressed defending infantry will be able to inflict casualties on them with direct aimed fire. The attackers will be able to inflict suppression in return, but probably few if any casualties; "it is next to impossible to inflict loss on men behind cover with direct rifle fire“ according to Sir Andrew Skeen (Passing it on, Bhavana, 2000). Suppression is, though, enough to conduct fire and movement to get an assault group close enough to assault the enemy position.
As the attackers close the enemy position, the last safe moment for supporting indirect fire will occur at some point. For medium artillery such as the now-universal 155mm, this might be 4-500m away, so this fire should have ceased before the EFL was crossed. For 105mm, 250m or so means that most of the fire and movement phase will rely on the attacking infantry’s own weapons. During WW2, British infantry were trained to follow up 25-pdr fire as close as 25m, and at Alamein at least one Scottish battalion advanced through its own barrage.
This phase may end in one of three ways. The attackers may not succeed in getting forward; the defenders may decide to withdraw. If neither of these occur, then the final assault will decide things.
At about 30m, another phase change occurs, and the defenders will start to take serious casualties. Hand grenades become effective at this range. It seems that, typically, once this phase has been reached the defenders will be defeated. This is why Ardant du Picq (Etudes sure le Combat) pointed out that it was not only the French army who boasted that “the enemy cannot resist our steel”, but every army in Europe; and they were all correct. Nor does the number of men in the assault group seem to need to be large. At Spion Kop, only a dozen or so South Lancs with fixed bayonets finally decided the day. Rommel (Infanterie Greift An) always favoured, and always succeeded with, a large base-of-fire element and a small assault element.
Close Quarter
Battle
Approach
Fire and Movement
Long range
300m
30m
Objective

5. Pattern of Ranged Fire Effect
Area Fire
Attacking
personnel
Point Fire
Guns, MGs, GMGs, Mortars
Small Arms
Hand Grenades
Point Fire
Vehicles
Guns, ATGW
RPGs
ATk Grenades
Now let us add vehicles into Speight and Rowland’s pattern.
Let us also consider the types of weapons fire capable of harming personnel and armoured vehicles.
Modern anti-tank weapons can hit and kill AFVs at ranges of 3000m and sometimes even further – this becomes principally a limit of bad weather and masking terrain. Therefore, while personnel are too fleeting and elusive to make other than area targets beyond 300m, vehicles are potentially vulnerable to point aimed fire to the limit of vision – they cross the EFL as soon as they come into sight.
Attacking personnel below ~300m are vulnerable to almost any weapon on the battlefield, and the general tendency is for things to get more dangerous, from direct fire at least, the closer to the objective one approaches.
Attacking armoured vehicles, on the other hand, as well as being largely safe from indirect fire. are potentially vulnerable to only a limited number of direct-fire weapons. The most dangerous of these range to the limit of vision. While things may get more dangerous with a closer approach to the objective, the tendency is less marked than for personnel. The threat of RPGs to ~300m means more weapons are in play, but they are no more effective than weapons that had to be reckoned with out to ~3000m.
Hand-thrown
Weapons
Heavy Weapons
Hand-held Weapons
3000m
300m
30m
Objective

6. Observations and Deductions
Vehicles are relatively invulnerable to area fire
Deduction: Obscurants have more value for vehicles than for personnel
Attacking infantry are relatively safe from point fire over ~300m
Vehicles approaching within ~3000m of the objective and in line-of-sight may expect to be engaged by tank guns or ATGW (capable of perforating up to ~1000mm RHAe)
Deduction: Vehicles lacking MBT levels of armour need to hide
Vehicles closing below ~300m risk attack from RPGs (capable of perforating up to ~750mm RHAe) carried by any individual infantryman
Deduction: Need high confidence that the objective is reliably suppressed
The further the infantry have to walk, the slower the pace of attack
Deduction: It is desirable to debus as close to the objective as possible
Another, slightly mathematical, deduction is that one should expect Lanchester’s linear law to apply to attacking infantry beyond ~300m and defending infantry beyond ~30m, and the square law at closer ranges, and for vehicles at all ranges. The fact that armour, unlike infantry, can achieve concentration of force without proportionally concentrating vulnerability suggests one reason for Guderian’s emphasis on using armour concentrated.
The typical pace of dismounted attack during WW2 is suggested by figures given in NA piece number WP 291/1169, An Analysis of Infantry Rates of Advance in Battle. Of the figures given for company attacks in daylight, the fastest achieves a rate of advance of km/h over a distance of half a mile (730m). The average for North Western Europe against slight opposition over short distances is 51 minutes to cover 730 metres, or 0.86 km/h. Attacks in Italy seem to have taken about 30% longer.

7. Fire and Movement – Balanced or Unbalanced Elements?
To cover the ground from the effective fire line to the objective, infantry has for the last 100 years employed Fire and Movement
One element provides a base of fire while another assaults
Elements specialised to one role or able to swing between them
1937, British infantry platoon reorganised
from 2 x Lewis sections (base of fire) + 2 x rifle sections (assault)
to 3 x Bren-equipped rifle sections (both roles)
1987, British infantry section reorganised
from gun group (base of fire) + rifle group (assault)
to 2 x balanced fireteams (both roles)
Commando 21, Royal Marine Commando reorganised
from 4 x rifle companies (both roles)
to 2 x Close Combat companies + 2 x Distant Combat Companies
“Rule of three” or “Rule of four” principles of organisation were universal in infantry organisations in WW2, with the exception of some specialised seaborne assault units (British Commandos, US Rangers, Japanese SNLF, Italian San Marco Battalion).
Most armies of WW2 fielded a battalion consisting of three rifle companies and an MG company. The British army were exceptional in having four small rifle companies, very few MMGs (MMGs were held by one specialist MG battalion per infantry division), and a carrier platoon (with similar automatic firepower to a rifle company) for each battalion.
Some armies fielded a heavy weapons platoon at company level, many did not. The US favoured weapons platoons, employing “light” (although tripod-mounted and therefore medium in British terms) machine guns at this level, so compensating for the shortcomings of the BAR as a section automatic.
The pattern of platoon organisation in most armies between WW1 and WW2 was to have a platoon consisting of four sections, two armed with an LMG. The Italians retained this organisation during WW2, but with two LMGs per LMG section. Most other armies issued an LMG to each rifle section in the platoon, making sections capable of both base-of-fire and assault roles. The Japanese, unusually, gave each platoon a light mortar section.
The idea of fireteam organisation originated with the Chinese, and was borrowed from them by the USMC. The US Army adopted fireteams in the 1950s, as a result of ideas put forward in J C Fry’s Assault Battle Drill. Fry had used fireteam organisation informally and successfully in combat in Italy with the 88th Division. This kind of informal organisation has probably been used for most of the 20th century; in the closing stages of WW1, British infantry “soft-spot” tactics acknowledged ad-hoc small groups known as “blobs”, an idea that survived at least until my time in the Territorial Army at the end of the 1970s.
For a good description of informal, rather than “by the book” organisation for combat, see Lionel Wigram’s letter from Sicily in Denis Forman’s To Reason Why. Barry Basden’s book Crack and Thump describes his successful use of British-taught battle drills by a junior officer in the US Army. Finally, note that British infantry often take the field in “multiples” rather than whole platoons, harking back to the WW1 German “Halb-Zug” organization.

8. Simpkin’s Dismount Triangle
After R E Simpkin, When the Squad Dismounts, Infantry 73[6], Nov-Dec 1983
Independent Action
Zulu Warriors,
Bronegruppa
Debussing means:
Risk of disorientation
More callsigns on the net
Does the leader dismount?
PanzerGrenadier
tradition
Using IFVs in an independent role tends to confirm Richard Ogorkiewicz’ original opinion of the BMP as a light tank with an infantry-carrying capability. But why not use light tanks in that role? When the other side has no armour, any tank is a super tank, and one of Dupuy’s historical surveys on the employment of light armour since WW2 has pointed out that recce vehicles are very often employed in non-recce roles. This is the tank in its original role as “battlefield bully”. Starry’s account of the ARVN use of M113s (Armor in Vietnam) makes it clear that they were not employed as APCs, but, with reduced crews, added armament and improvised gunshields, as light tanks.
Alternatively, if the IFV has a long-range ATGW, it may draw off and attempt to contribute to the tank fight. Good luck with that.
In the intimate support role, IFVs might still be acting as battlefield bullies, but as infantry tanks. In effect they are an armoured gun group for the dismounted rifle group.
Withdrawing to a Zulu muster doesn’t give the carriers much to do, and increases the time it will take to get back and reembus the troops.
One of the advantages of open tops – and perhaps firing ports, though I doubt it – is that they let the troops know something of what is happening outside the vehicle. As a minimum, they should be able to listen in on the vehicle’s radio. However, emerging into the sunlight, and perhaps the firefight, is bound to be potentially confusing.
If your Combat Net Radio runs an automated position reporting scheme, the doubling or tripling of callsigns on dismounting might cause problems beyond extra traffic on the voice net.
Does the section leader dismount? I have been unable to find national policies on this, and it seems to be left to his discretion. I would argue that as the prime function of an IFV is to provide infantry close combat capability, he should be outside the vehicle on his feet saying “Follow me”.
Battle Taxi
tradition
Intimate Support
Withdraw to Zulu Muster

9. How Far From the Objective to Debus?
WW2 British guidance for the Carrier Platoon: When in doubt, dismount
“Old Blood and Guts”: Armored Infantry should not attack mounted [Letter of Instruction No. 2, 3 April 1944]
Dismount should take place after deployment into combat formation, as close to the FEBA as possible [V Pishakov and L Kirpach, BMPs in Battle, Voennyi Vestnik no , quoted in Kosevich 1977]
But consider US 9th Div experience with helicopter assaults in Vietnam: Lieutenant Colonel Fred Mahaffey…refined the operations of the battalion until in Long An Province insertions were made no farther from the target than 100 meters and in some instances as close as 15 meters. This was pushing the balance of the risk of a hot landing zone against the achievement of total surprise to the limit. However, the technique paid off as during the period of a year no lift ships were lost. [Ewell and Hunt, Sharpening the Combat Edge]
Obviously, if there is a good debussing point you can reach via a covered approach, you do that. It is the variations in terrain that make every section, platoon or company attack different from all the others.
But the “battle taxi” tradition favours early and precautionary dismounting, and even Patton does not think armored infantry should attack mounted.
Official US doctrine of the time, however, agreed with the Russian gentlemen quoted; dismount as late as possible.
The 9th Div helo experience points up the counter-intuitive advantage of closing right up to the objective, even in something a vulnerable as a helicopter (in this case UH-1s, first-generation turbine helos with no armour apart from the flak jackets of the pilots and door gunners). Evidently, this requires reliable suppression of the objective.

10. What Makes Good Armoured Infantry?
WW2 German tactical policy demanded rapid transition between mounted and dismounted operations
We had this constant debussing and re-embussing [Maj Simon Knapper, OC A Coy Staffordshire Regt, quoted in Rat’s Tales]
Moving and fighting at tank tempo matters
A tanker halts between moves; an infantryman moves between locations [Richard Simpkin, Mechanized Infantry]
Does the IFV need to be able to join the long-range tank fight?
…defense analysts, preoccupied with the Russian tank threat, wished to convert the MICV into a primary tank killer. This tendency was reinforced by the fact that the simulation models available to the analysts were never able to cope with the complexity or even the role of the mechanized infantry, and focused on the battles between tanks and antitank weapons. For years all the simulation war games ended before the first infantry became involved. [Benjamin Freakley, Interrelationship of Weapons and Doctrine: the Case of the Bradley Infantry Fighting Vehicle]
Operating in support of armour means operating at armour pace, and in particular this means not bogging down with protracted dismounted approach marches or assaults. Nor should the vehicles depart to a Zulu muster, as that will slow things further.
“An army advances as fast as it thinks” – tempo depends on attitude of mind at least as much as it does on equipment.
The idea of mounting ATGW on ordinary IFVs does not seem to me to be a good one. This is one place where I think the British army has got it right, along with the French and the Israelis, and the Americans and Russians wrong (the Germans are half-and-half, as their ATGW are dismountable section weapons).
What was the reasoning for ATGW? For the Russians, I suspect a sop to Khrushchov’s boyish enthusiasm for rockets of all kinds. For the Americans, we have the evidence quoted here that it was a defence analysis cockup, in which simulationists, sadly, are implicated. When Gen DePuy was presented with the choice of Bradley with TOW or no Bradley at all, he understandably chose the former; but that was not what the US Army had originally specified.
One of the big disadvantages of carrying ATGW in an IFV is that they can have horrible effects on survivability. Quite apart from encouraging you to participate in the tank fight, a TOW (say) carries a lot of energetic material, and is stowed high in the turret.

11. The Vehicle Protects Against What?
Weapons fire at some level
Traditional APCs – rifle-calibre small-arms and indirect fire fragments
Modern IFVs – maybe 14.5mm all-round, 30mm autocannon frontally
Israeli HAPCs perhaps better than MBT protection
Against top-attack weapons a DAS is needed
Mines
Cold War veterans will recall the importance assigned to
Chemical weapons
Residual nuclear radiation
The embussed section is also protected against
Fatigue [consider Marshall’s The Soldier’s Load]
Suppression [the main effect of most weapons against infantry]
Dispersion [they’re all in the same box]
In Lebanon in 2006,
More IDF infantry were killed by ATGW outside vehicles than inside
Modern armour might be modular so that you can armour to specific threats. Of course this affords the Treasury the possibility of procuring lots of vehicles fitted “for, but not with” worthwhile armour.
The mine threat has had troops riding on top of the vehicle, outside the armour, both in Viet Nam and during the Russian involvement in Afghanistan.
The inadequate protection levels of the BMP family, as shown up by combat experience in the 1973 Yom Kippur War and since, is probably due to its originally being conceived as a vehicle for nuclear warfighting. There is little need to worry about an enemy direct-fire threat if the defensive position has been turned into a big glass ashtray by a bucket of tactical instant sunshine, and firing ports probably make more sense if they are intended only for taking pot-shots at the odd survivor in the Sarin-soaked wasteland outside.
A neglected aspect of the protection afforded by armour is the fact that it protects its passengers from fatigue, suppression and dispersion (and hence disorganisation). Fatigue is a very important factor; Marshall (The Soldier’s Load) showed that it is fungible with fear – tired men scare more easily, scared men tire more easily. Arriving at the assault position fresh is therefore quite an advantage, the more so if one considers the weight of combat body armour (CBA). I would suggest that CBA is a sensible thing for Panzergrenadiers to wear, but not normally for “leg” infantry.
Protecting soldiers from suppression and disruption is also a considerable benefit. While there might be a risk of disorganization on debussing, this must be weighed against the opportunities for disorganization presented by trying to advance by fire and movement over a couple of hundred metres under fire. Ardant du Picq (Etudes sur le Combat) said “the closer we get to the enemy, the further we get from each other”: if everyone is in the same box, there is no choice in the matter.
As well as these things, a vehicle protects from ammunition depletion. Soldiers have historically carried only sufficient ammunition for five or six minutes’ worth of rapid fire, and even with micro-calibre rounds permitting basic loads of 300 rounds per rifleman, that might still easily be expended in ten minutes. With LMGs the problem is worse yet. But ammunition loads that would weigh down a section on its feet can be carried many times over on a vehicle.

12. Firing Ports, or a V-shaped Hull?
Firing ports have been tried in:
Sd Kfz 251 Ausf A (dropped in Ausf B)
M113 in Vietnam (not used)
BMP-1 and BMP-2 (only 2 left in BMP-3)
Marder 1A1 and 1A2 (dropped in 1A3)
M2 and M2A1 Bradley (only 2 left in M2A2)
This business of social cohesion seems to me to be better favoured by having everyone sit facing each other.
The V-shaped hull is useful for mine protection. This matters in all phases of war, but in high-intensity warfare it has generally been thought more important to achieve a low silhouette.
Firing ports seem always to evolve towards extinction, as per the examples. One may cite the analogous disappearance of pistol-ports from tanks after WW2 (as far as I am aware, the Koenigstiger and IS-2 were the last tanks to be designed to include pistol ports). On the other had, more armour often seems to be a welcome addition (BMP-2D in Afghanistan, Desert Warrior, FV432 Bulldog).
Is sitting back-to-back good
for group cohesion?

13. Other Close-In Weapons
WW2:
Nahverteidigungswaffe
S-mine launchers
Krummlauf assault rifle
Korea:
MGs in “scratch my back” mode
Canister rounds developed
Vietnam:
Claymorettes
.22 salvo boards
Now:
76mm grenade dischargers in Puma (based on Israeli experience)
Are dual-purpose close-in weapon/DAS munitions feasible?
There may be lots of things
flying around outside the
vehicle anyway:
Sabot petals
ERA plates
DAS projectiles
If you really want to engage enemy personnel close to the vehicle, there are better ways than firing ports.
The fact that the Israelis have chosen to go for a close-range grenade system suggest to me that it is a good idea.
Smoke grenades, DAS projectiles, claymorettes and close-in grenades seem to me all to be small, light munitions aiming to fill the air close-in with flying fragments (or smoke). Could these not be fired from a common launch system? Could you command-detonate an ERA panel as a claymorette? The Russians seem to consider a dual-purpose MG/CIWS feasible.

14. Could Vehicles Assault Under VT Fire?
Sydney Jary has criticised the increased safety distances needed as field artillery changed from 88mm to 105mm to 155mm
George Patton again: Tanks can move with perfect impunity under time fire provided by either 105mm or 155mm projectiles [Letter of Instruction No. 2, 3 April 1944]
A WW2 OR experiment showed that Churchill tanks could drive fairly safely through impact-fuzed 25-pdr: There is no adverse effect on the crew from a 25 pdr direct hit. Fragments cannot penetrate the tank, and the blast is not at all uncomfortable. [WO 291/399, Casualties to Churchill Tanks in 25-pdr HE Concentrations, 1943]
Another way of filling the air near your vehicle with small shards of flying steel is to get the gunners to do it.
Note that, although it did not have a reputation for being over-armoured, the Sherman had unusually thick roof armour.
It makes “the race to the parapet” a foregone conclusion if you can actually park your vehicle on the parapet while friendly artillery is still falling. The “last safe moment” could be when you de-bus on the objective. Obviously you will want high assurance in coordinating debussing with the cessation of both support fire and firing the close-in weapons just mentioned.

15. Achieving Shock
Rowland’s HA [The Stress of Battle] has shown that shock arises from
Intense bombardment
Achievement of surprise
Rapid approach of attackers
Poor visibility
Perception of invulnerability of enemy armour
Deduction: Driving fast through smoke behind heavy armour to debus on the enemy position immediately after a VT bombardment ticks all the shock boxes
The thickness of armour protection could itself be a shock factor.
Speed of approach certainly is.
Thus, attributed of the HAPC that appear defensive may, in their effect, be offensive, in that they contribute to shock. I think we want not a vehicle for the infantry to fight in, but a vehicle for the infantry to assault from: doesn’t “Infantry Assault Vehicle” sound better than HAPC?

16. How Many Kinds of Infantry?
In WW2 the BLA had
Motor Battalions (Half-tracks and carriers)
Lorried Infantry Battalions (TCVs)
Infantry Battalions (lifted by RASC coys or Kangaroo sqns)
Recent British terminology distinguished
Armoured Infantry (IFVs)
Mechanized Infantry (APCs)
Light Infantry (trucks)
With Army 2020 we seem to be moving towards
Heavy Protected Mobility Infantry (Heavy MRAPs)
Light Protected Mobility Infantry (Light MRAPs)
Light Infantry (trucks) – in Adaptable Force only
“How many kinds of infantry” seems to be poorly co-ordinated with the naming of infantry.
In WW2, the US army had infantry divisions and armored divisions, and the infantry in its armored divisions were called armored infantry (and eventually got preferential pay scales). After WW2 the name was changed to mechanized infantry, and the same name is used whether riding in IFVs or APCs.
The Russians in WW2 had motostrelki (motor rifle) troops in tank corps and mechanized corps, but these all rode in trucks (or on the backs of tanks). APCs only began to appear after Once the BMP appeared there was a clear two-tier organisation of infantry, but all were given the same motor rifle designation.
The Germans originated the Panzergrenadier concept in WW2, but, again, used the same name when there was a clear distinction in role and equipment. Only a favoured few rode in armoured half-tracks, the others, mounted in softskin vehicles, being charmingly known as Gummipanzergrenadiere.
The British approach was more eccentric, as above. An armoured division had two brigades, an armoured brigade with an integral motor battalion, and a lorried infantry brigade, in TCVs. The recent distinction between Armoured, Mechanized and Light infantry is I think clearer than anyone else’s naming system. I can see no essential difference in role between PM Hy, PM Lt and Light infantry battalions – they just have different kinds of battle taxi.

17. Who Owns the Vehicle? WW2:
Fr Dragons Portés, Ge PanzerGrenadiere, US Armored Infantry, Br Motor Bns and Lorried Inf Bns owned their own vehicles
US and British infantry used pooled trucks
British and Canadian infantry used pooled Kangaroos
Post-war:
Soviet and British APCs pooled until mid-1950s
ARVN and Australian APCs still pooled during Vietnam War
Now the vehicle seems always to belong to its passengers (“Battle Winnebago” rather than “Battle taxi”)
If an APC were really a battle taxi, then, rather than head off to a Zulu Muster once it had dropped off its passengers, it would go and pick up another fare. This might not need to be infantry; you can always bring up CSups and backload casualties, as carrier platoons did in WW2. Pooled APCs might also appeal to the Treasury as an economy measure.

18. How Many Kinds of ICV? Firepower Protection Transport T MBT *** *** --
BTR
APC * *
***
BMP
IFV ** ** **
BTRT
HAPC *
***
***
BMPT
TSV **
*** --
A fairly clear distinction is between light and heavy APCs and IFVs.
The tank is not an ICV, and the TSV is really a resurgence of the female tank.
The light APC and light IFV are long-established classes of vehicle.
The HAPC (which the Kangaroo was) has been adopted by Israel, Russia, India, Jordan. It seems a sensible use of last-generation tank chassis if you want to do things on the cheap, although the Israelis seem to have decided that building new was preferable for the Namer.
The classes I think you really need are a HAPC (I would call it an IAV) for armoured infantry and a thin APC, probably wheeled, possibly pooled, for ordinary infantry. The lightly-armoured IFV, especially if ATGW-equipped, I think is a mistake, based on muddled doctrinal thinking.
BTMP
HIFV
***
*** *
You can’t have all of heavy armament, heavy armour, and transport a full section

19. Or Can You Have it All? BTMP-84: 125mm gun with 30 rounds ATGW capable
14.5 and 7.62 MGs
MBT armour (T-84)
3 crew, 5 dismounts
48.6 tonnes
I sometimes think Ukrainian weapons designers have been too much influenced by not having a Johnny 7 One-Man Army when they were small.
Notice that nobody has ordered this thing yet.

20. Must We Dismount a Whole Section?
HS-30: 5-man dismounted gruppe
BMP:
BMP-1: 8-man dismounted section
BMP-2 and -3: 7-man dismounted section
Bradley:
Initially 3 dismounted squads of 6
Then 2 dismounted squads of 9, split across vehicles
Now 3 dismounted squads of 9, split across vehicles
Warrior: 7-man dismounted section
Marder: 7-man dismounted gruppe
Puma: 6-man dismounted gruppe
BTMP-84: 5-man dismounted section
Can we treat the IFV as an “armoured gun group”?
Who remembers Exercise SEA WALL?
Wanting to have heavy armament on an IFV – two-man turret and 30-40mm cannon – tends to decrease the number of passengers to below the normally-accepted size for a squad. In particular, this has done terrible things to US infantry platoon organisation, which I suggest would not be battleworthy against a first-class enemy. Whatever it is I want to do on dismounting, a compulsory reorg isn’t it. Better go with the small squads as was originally the case.
Smaller section size does not matter if you are in the “intimate support” corner of Simpkin’s dismount triangle.
If you recall Jim Storr’s magnificent article on his Sea Wall experimental platoon organisation (BAR 119) you will know that there is a case for organising the platoon as four five-man sections plus HQ, and abolishing the fireteam level of command. I would argue that, apart from its merits as argued by Storr and its convenience for vehicle-portability purposes, such an organisation is quite close to the 4-brick multiple that has become a de facto standard in British Army operations since its original use in Op Banner.

21. In-House Infantry
Simpkin proposed that tank-accompanying Hausinfanterie
Have the main task of ensuring the tanks can get forward
Need to be able to undertake assault pioneer tasks
Need to have a mobile mentality
Should be permanently grouped with the armour (cf Swedish Mech Inf)
Need not be cap-badged infantry (cf Austrian Waffenfarbe)
These requirements are quite different from providing protected mobility for an ordinary infantry battalion:
Beginning in the 1970s, the post-war recovery of European infantry was cut short by the widespread introduction of infantry fighting vehicles. Essentially small tanks with compartments for a handful of infantrymen, infantry fighting vehicles are useful for such tasks as providing anti-infantry and anti-antitank protection for main battle tanks, reconnaissance for armoured formations, and escort services for convoys. Their immediate effect on infantry equipped with them, however, is to convert those units to something other than infantry. This is done by reducing both the size and number of rifle squads and making the remaining infantry teams dependent on their vehicles for everything from transport to covering fire. – English & Gudmundsson.
I think there should be two kinds of infantry. Neither of them should fight mounted.
The first kind – mounted infantry, motor rifle, mechanized infantry, armoured infantry, all are honourable names – should have as their prime duty getting the tanks forward. They should (like RAC assault troopers) be permanently grouped with their tanks, and share the mentality of “pausing between thrusts”. They should only fight dismounted, but should do so in swift, shocking assaults from their vehicles and in close cooperation with them. They should be quick to re-mount and crack on. These are the “something other than infantry” English and Gudmundsson mention. They are indeed dependent on their vehicles – it is the section/vehicle combination that is the fighting element.
The second kind are “ordinary” (I am tempted to say “proper”) infantry. They rely for protection not on armour, vehicular or personal, but on fieldcraft in advance and attack and fieldcraft plus field fortifications in defence. They can operate in complex terrain inaccessible to AFVs, and can be transported to (but not in) battle by truck, APC or helo. When tanks operate with them, it is the tanks who support the infantry.
Motor rifles (or whatever we call them) are not limited by their ability to carry weight over distance. CBA and full-automatic weapons make perfect sense for them, and they probably only require light, close-range, micro-calibre small arms, as they have their “armoured gun group”.
Infantry of the footslogging kind must be extremely careful about weight, especially as they may have to man-pack their own heavy weapons. They might need personal weapons able to dominate the “infantryman’s quarter-mile”, and will simply not be able to carry CBA, big fat radios and loads of batteries and retain the ability to manoeuvre.
The motor rifle role is only really applicable to high-intensity warfare, where armoured combat is required. “Ordinary” infantry, on the other hand, have a role across the entire spectrum of conflict. Although they benefit from the support of other arms, they can if necessary function alone, which no other arms can do. They are the slowest, most vulnerable, lowest-tech of all the combat arms. They will take most of the casualties, and their organisation should make allowance for this. But it is upon them that victory finally depends, because you cannot control ground until your infantry can walk across it, and the enemy’s cannot.
“In war, possession is ten points of the law, and the infantry are the bailiff’s men”.

22. Bibliography
Anon, The Cutting Edge: Soviet Mechanized Infantry in Combined-Arms Operations, Research Report CIA SOV D, Directorate of Intelligence, October Benson, Nicholas, Rat's Tales: The Staffordshire Regiment at War in the Gulf, Brassey's, London, Braun, G J, The Infantry Tank: Experiences Based on the British Maneuvers, 1935, Review of Military Literature, Vol 16 No. 61, June 1936 English, John A and Gudmundsson, Bruce I, On Infantry, Praeger, Westport CT, Ewell, Julian J, and Hunt, Ira A, Sharpening the Combat Edge: The Use of Analysis to Reinforce Military Judgement, Department of the Army, Washington DC, 1974, FM 17-42, Armored Infantry Battalion, War Department, Washington DC, November Freakley, Benjamin C, Interrelationship of Weapons and Doctrine: the Case of the Bradley Infantry Fighting Vehicle, School of Advanced Military Studies, US Army Command and General Staff College, Fort Leavenworth KS, December Gajowski, Matthew, German Squad Tactics in WWII, Nafziger, Pisgah OH, Gibbons, Edward G, Why Johnny Can't Dismount: The Decline of America's Mechanized Infantry Force, School of Advanced Military Studies, US Army Command and General Staff College, Fort Leavenworth KS, December Grau, Lester W, Preserving Shock Action: A New Approach to Armored Maneuver Warfare, Armor, September-October Held, Bruce J, Lorell, Mark A, Quinlivan, James T, Serena, Chad C, Understanding Why a Ground Combat Vehicle That Carries Nine Dismounts Is Important to the Army, RAND Arroyo Center, Hugin, MICVs/IFVs or Mini APCs?, British Army Review 118 April Jary, Sydney, and Carbuncle, A Mitigated Blessing: Protected Mobility for Infantry, British Army Review 118 April Kershaw, Robert N, It Never Snows in September, Crowood Press, 1990; Ian Allan, Hersham, Marshall, S L A. The Soldier’s Load and the Mobility of the Nation, Combat Forces Press, Washington DC, 1950; Marine Corps Association, Quantico, VA, 1980.
Ney, Virgil, The Evolution of the Armored Infantry Rifle Squad, CORG Memorandum CORG-M-198, US Army Combat Developments Command, Fort Belvoir, VA, March 1965.
Ogorkiewicz, Richard M, Armour, Stevens & Sons, London, 1960.
Ogorkiewicz, Richard M, Mechanized Infantry, Military Review, August 1974.
Ogorkiewicz, Richard M, Future Combat Vehicles: The Technological Possibilities, RUSI Journal 146[4], 2001.
Ogorkiewicz, Richard M, Tanks: 100 Years of Evolution, Osprey, Oxford, 2015.
Patton, George S, War As I Knew It, Houghton Mifflin, New Yotk NY, 1947, 1995.
Rowland, David, The Stress of Battle: Quantifying Huma Performance in Combat, TSO, May 2006.
Simpkin, Richard E, Mechanized Infantry, Brassey's, Oxford, 1980.
Simpkin, Richard E, Deep Battle: The Brainchild of Marshal Tukhachevskii, Brassey's, London, 1987.
Simpkin, Richard E, When the Squad Dismounts, Infantry 73[6], Nov-Dec 1983.
Speight, L R, Rowland, D, Modelling The Rural Infantry Battle: Overall Structure and a Basic Representation of the Approach Battle, Military Operations Research 11(1):5-26, November 2006.
Starry, Don A, Mounted Combat in Vietnam, Department of the Army, Washington DC, 1978, 2002.
Storr, Jim, Exercise SEA WALL: Infantry Tactics in the Era of Manoeuvre Warfare, British Army Review 119, August 1998.
Wise, Sidney, Convoy Counterambush Weapon Systems, US Army Limited War Laboratory, Aberdeen Proving Ground, MD, March 1966.
WO 232/77, Communications within the Infantry Battalion, November 1944 to June 1945.
WO 291/399, Casualties to Churchill Tanks in 25-pdr HE Concentrations, 1943.
Zaloga, Steven, Soviet/Russian Armor and Artillery Design Practices: 1945–1995, Marine Corps Intelligence Activity, Quantico, VA, September 1996.
Considering what a large proportion of the ground forces of most advanced nations is made up of mechanized or armoured infantry, it is astonishing how slender is the literature on the topic; especially when one compares it to the vast resources available on tanks, artillery and infantry weapons.

23. Any Questions?
Dr John D Salt Centre for Simulation and Analytics Cranfield University Defence Academy of the United Kingdom Shrivenham SN6 8LA