2.  Two armies are camped on the outskirts of either side of an enemy city.

4.  The generals of the armies can only communicate via messengers who must travel through enemy territory and are thus subject to delays or capture.

5. Message

6. Acknowledgeme nt Message

7.  The two generals have previously agreed on a plan of attack, but they must communicate to set up the attack time.  If one army attacks but the other doesn’t they will be defeated and then the enemy city will defeat the other army.

8.  If the first general decides to send the message saying, ◦ “Let’s attack at noon tomorrow”

9.  One of three things could happen ◦ Scenario 1 ◦ Scenario 2 ◦ Scenario 3

10.  SCENARIO 1 The message could intercepted when it is being sent to the second general

11. Message

14.  SCENARIO 1  So what?  Well Army1 will attack at noon, but Army2 won’t.  Army1 will be defeated.  Army2 will be attacked and defeated.

15.  SCENARIO 2  The message could be received by the second general but the acknowledgement that is sent back could be intercepted.

16. Acknowledgeme nt Message

17. Acknowledgeme nt Message

18. Acknowledgeme nt Message

19.  SCENARIO 2  So what?  Well Army2 will attack at noon, but Army1 won’t know if the message was received so Army1 won’t attack in case Army2 doesn’t.  Army2 will be defeated.  Army1 will be attacked and defeated.

20.  SCENARIO 3  The message is received by the second general and the acknowledgement is sent back.

21. Acknowledgeme nt Message

22.  SCENARIO 3  So what?  Army1 and Army2 attacked together, and defeat the enemy.

23.  In groups of three or four, think of five ways to help ensure that both armies attack together.