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Mexican War: Introduction and Causes

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1 Mexican War: Introduction and Causes
Lsn 2

2 ID & SIGs Manifest Destiny, Polk, Scott, Taylor, Texas, Wilmot Proviso, California,Tyler, Slidell, Benton, Whigs, Jomini, West Point, artillery tactics, infantry tactics, volunteers

3 Manifest Destiny Settlers began flocking west in search of cheap land
“(It is) ...our manifest destiny to over spread and to possess the whole of the continent which Providence has given us for the development of the great experiment of liberty.” John O’Sullivan, editor of the “The Morning Post,” 1845

4 Texas US foreign policy of expansion (Manifest Destiny) soon put it in conflict with Mexico American immigrants moved to Texas when it was still a province of Mexico and began clamoring for independence After initial setbacks at the Alamo and Goliad, the Texans defeated the Mexican Army at the Battle of San Jacinto on April 21, 1836 and Texas declared its independence from Mexico Before he left office, President Andrew Jackson extended diplomatic recognition to Texas but, fearing war with Mexico, refused its request to be annexed to the US

5 Texas Jackson also knew that annexing Texas, a potentially huge area for the expansion of slavery, would hurt fellow Democrat Martin Van Buren’s chances of election in 1840 Nonetheless, Jackson privately urged Texans to seize harbors on the Pacific Coast which made annexation more attractive to commercial interests in the northeast Andrew Jackson

6 Texas William Henry Harrison ran for President as a Whig and defeated Van Buren The strongest Whig areas were in the New England and Great Lakes area so Harrison balanced his ticket regionally with Virginian John Tyler as a vice-president When Harrison died of pneumonia in April 1841, barely a month after his inauguration, Tyler became president Harrison

7 Texas Tyler was a former Democrat who had left the party over Jackson’s issuance of the Force Bill during the Nullification Crisis Tyler’s agenda strongly supported the South and state’s rights He began distancing himself from the Whig agenda and renewed the annexation of Texas issue to gain favor with southern and western Democrats John Tyler

8 Texas Tyler replaced Daniel Webster as secretary of state with pro-annexation Virginian Abel Upshur and secretly opened negotiations with the Texans After Upshur died, John Calhoun became secretary and completed the negotiations and made the protection of slavery a highly visible issue Calhoun saw the annexation of Texas as a security issue for the United States and accused the British of conspiring to force emancipation on Texas and destroy slavery in the South

9 Texas Calhoun’s rhetoric convinced antislavery northerners that the annexation of Texas was part of a southern plan to expand slavery and political power The Senate rejected Calhoun’s treaty of annexation by a two-to-one margin in June 1844, but the debate continued John Calhoun

10 Texas In the Election of 1844, Van Buren’s anti-annexation stand cost him the Democratic nomination Instead it went to James Polk, a compromise choice from Tennessee who favored expansion (both in Oregon and Texas) Tying Oregon to the expansion package helped protect the Democrats from being accused of being too prosouthern

11 Texas Polk defeated Whig candidate Henry Clay by less than 2% of the popular vote, but Tyler still took Polk’s victory to be a mandate to annex Texas Rather than putting the matter before the Senate where he knew he could not muster the necessary 2/3rds majority, Tyler used a joint resolution of Congress to invite Texas to join the Union Mexico, of course, did not consider the annexation legitimate

12 Diplomatic Machinations Eve of Mexican War
Many Americans, including Polk, had expansionist designs not only in Texas but on Upper California and New Mexico as well Mexican authorities had only tenuous control of these areas Possession of San Francisco would give the US a valuable harbor to support trade with the Far East Democratic Senator Thomas Hart Benton of Missouri was a key proponent of gaining Pacific Coast harbors to further trade with India and China

13 Diplomatic Machinations Eve of Mexican War
Polk dispatched John Slidell to Mexico City with an offer to purchase California and New Mexico and to secure the Rio Grande as the Texas boundary The Mexicans considered the Nueces River to be the border between Texas and Mexico while the Texans considered it to be the Rio Grande

14 Diplomatic Machinations Eve of Mexican War
Slidell landed at Vera Cruz on November 29, 1845 but Mexican foreign minister Manuel Pena y Pena announced he would receive Slidell only as a “commissioner” rather than as a full-fledged “minister” The Mexicans felt that granting Slidell status as minister would give credence to the American claim to Texas and weaken General Jose Herrera’s government

15 Diplomatic Machinations Eve of Mexican War
Slidell arrived at Mexico City on December 6, but the Mexicans refused to meet with him as long as he insisted on being considered a minister In January 1846, Slidell notified Polk that he had given up on a diplomatic solution John Slidell

16 US Political Scene on Eve of Mexican War
Even while Slidell was trying to negotiate, Polk was preparing for military action In June 1845, Brigadier General Zachary Taylor was ordered to prepare to move his army from Fort Jessup, Louisiana, into Texas. In July, Taylor began moving by land and water to Corpus Christi For the next seven months, Taylor trained his men at Corpus Christi

17 US Political Scene on Eve of Mexican War
With the diplomatic failure, Secretary of War William Marcy notified Taylor on January 13, 1846 to “advance and occupy, with the troops under your command, positions on or near the east bank of the Rio del Norte [the upper or New Mexico section of the Rio Grande]”

18 US Political Scene on Eve of Mexican War
The Mexicans and Americans stared at each other across the river for two weeks In April, the Mexicans attacked an American scouting party Taylor informed Washington, “Hostilities may now be considered as commenced.” Congress declared war on May 18, 1846

19 US Political Scene on Eve of Mexican War
Wilmot Proviso Introduced by Pennsylvania Congressman David Wilmot on August 6, 1846 to prohibit slavery in any territory gained from the war with Mexico Approved by the House but rejected by the Senate Reintroduced in February 1847 with the same result Cartoon depicting the divisive effects of the Wilmot Proviso

20 US Military on Eve of Mexican War
Because of the soft support for the war, especially in the northeast, Polk decided to avoid large-scale use of the militia Authorized the raising of 50,000 volunteers, mostly from the southern states Authorized Regular Army to double its existing size to 15,000 by filling units up to full strength President James Polk

21 US Military on Eve of Mexican War
America got most of its military ideas from Europe Antoine-Henri de Jomini ( ) was a Swiss military theorist who sought to interpret Napoleon Published the Summary of the Art of War in 1838 Became the premier military- educational text of the mid- nineteenth century

22 US Military on Eve of Mexican War
As a product of the Enlightenment, Jomini sought natural laws to govern the conduct of war Developed a very geometrical and scientific approach to war Stressed the principle of concentration, the decisive point, the strategic value of interior lines, and the close relationship between logistics and combat Interior lines are “those adopted by one or two armies to oppose several hostile bodies, and having such a direction that the general can concentrate the masses and maneuver with his whole force in a shorter period of time than it would require for the enemy to oppose them a greater force.”

23 US Military on Eve of Mexican War
The benefits of interior lines could be gained either by central position or superior lateral communications Interior Lines Exterior

24 US Military on Eve of Mexican War
In 1835, Winfield Scott’s three-volume Infantry Tactics was adopted by the Army Emphasized discipline over speed and mass over maneuver Stressed close-ordered lines of either two or three ranks and discouraged the use of any movement faster than the quick time rate of 110 steps per minute Loose order was allowed only in skirmishing tactics where advanced troops deployed forward of their main lines to cover their own troops and to develop the enemy’s fire.

25 US Military on Eve of Mexican War
Each regiment would have one company of rifles or light infantry to act as skirmishers for the entire regiment However, in Mexico, such skirmishers would be only deployed in small numbers as a reaction to terrain and circumstances Scott’s Infantry Tactics proved to be very appropriate for the situation in Mexico

26 US Military on Eve of Mexican War
Command and control was based largely on line-of-sight signaling, couriers, and audible signals Color bearers were critical to command and control The commander’s physical presence on the battlefield was not just a sign of bravery but also his most reliable means of control

27 US Military on Eve of Mexican War
Prior to Mexico, the Army had not had to deploy and had not had to worry about long supply lines Expanded transportation distances and demands in Mexico would make it “the first steamboat war”

28 US Military on Eve of Mexican War
The most common firearm in Mexico was the flintlock musket with a range of 100 to 200 yards The percussion cap Model 1841 Springfield was the official standard shoulder arm, but traditionalists like Winfield Scott thought the system was too complicated and the flintlock prevailed Less traditionalist volunteer units like Jefferson Davis’s Mississippi Rifles were willing to use the new technology

29 US Military on Eve of Mexican War
The US had pursued a vigorous program to build its artillery The 1841 system featured bronze smoothbores usually organized into a six-piece battery of four guns and two howitzers The six-pounder gun had an effective range of 1,523 yards

30 US Military on Eve of Mexican War
Following the example of the French and British, the US began organizing one company in each artillery regiment as light or “flying” artillery to be used with the infantry Because artillery could fire canister at about 400 yards compared to the musket’s range of about 100 yards, the artillery had “stand-off” The artillery could blast holes in enemy defenses while remaining out of range of the infantry Artillery in Mexico was often used offensively in close coordination with an infantry assault

31 US Military on Eve of Mexican War
Mexico was the first time the US Army was organized into divisions Units pioneered by Napoleon to facilitate semi-autonomous flanking movements The Army had a shortage of senior leaders capable of commanding these larger, more flexible units This deficiency was partly off-set by the small size of the units employed in Mexico and by the superior junior leadership

32 US Military on Eve of Mexican War
In 1817, Sylvanus Thayer replaced Captain Alden Partridge as superintendent of West Point and began reversing the damage Partridge had done. Thayer broadened and standardized the curriculum, established a system to measure class standing, organized classes around small sections, improved cadet discipline, created the office of commandant of cadets, and improved military training. “The Father of the Military Academy”

33 US Military on Eve of Mexican War
By the time of the Mexican War, Thayer’s reforms had produced a generation of men who would fill the junior officers’ ranks in Mexico. These lieutenants and captains stood in sharp contrast to the older officers who had not benefited from a systematic military education and training. The impact of Thayer and West Point was readily apparent in Mexico. West Point was founded in 1802 and was instrumental in training engineers in the 19th Century

34 US Military on Eve of Mexican War
Winfield Scott called his West Pointers his “little cabinet” Scott was unwavering in his acknowledgement of West Pointers declaring, “I give it as my fixed opinion that but for our graduated cadets the war between the United States and Mexico might, and probably would, have lasted some four or five years, with, in its first half, more defeats than victories falling to our share, whereas in two campaigns we conquered a great country and a peace without the loss of a single battle or skirmish.”

35 Key Players James Polk. President of the US. Staunch advocate of Manifest Destiny. Mexico is sometimes called “Mr. Polk’s War.” Thomas Hart Benton. Democratic Senator from Missouri. Considered for a lieutenant generalship by Polk to stave off the Whigs. Daniel Webster. Senator from Massachusetts. Example of Whig opposition to Mexican War.

36 Key Players Winfield Scott. Thoroughly professional officer and hero of the war of Ordered by Polk to open a second front to rival Taylor. Stephen Kearney. Conducted a easy campaign to seize New Mexico and then pressed on to secure California. Zachary Taylor. Veteran of the War of 1812 and Indian Wars. Ordered by Polk to the Rio Grande. Polk saw him as a political rival.

37 Key Players John Fremont. Was already in California on a mapping expedition. Helped secure the territory but refused to relinquish command to Kearney and was court martialed. John Sloat. Naval commander who helped Fremont secure California. Replaced by Stockton. Robert Stockton. Developed a naval blockade and assisted Kearney in the conquest of California.

38 Key Players Alexander Doniphan. Led a regiment of Missouri volunteers. Helped Kearney secure New Mexico then entered north Mexico. John Slidell. Polk’s appointed minister to Mexico. Mexico failed to recognize Slidell as such and negotiations failed. Nicholas Trist. Ran afoul of both Polk and Scott but ultimately negotiated the treaty of Guadalupe Hidalgo.

39 Key Players David Twiggs. Led main effort at Cerro Gordo. Scott felt Twiggs was “not competent to command an army in the presence of the enemy– nor its absence.” Gideon Pillow. Political general. Law partner of Polk. Exacerbated difficulties between Scott and Polk. John Wool. Division commander at Saltillo and Buena Vista. Maybe the best division commander but still unremarkable.

40 Key Players William Worth. Served first under Taylor, then joined Scott. Had some talent, but also a quarrelsome personality. Jefferson Davis. Commanded the Mississippi Rifles, winning fame at Buena Vista and showing the value of the rifle. Robert E. Lee. Member of Scott’s staff. Representative of the role played by engineers and West Pointers.

41 Next Lesson Zachary Taylor

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