Strategic Error in the Illiad

When the dissension stroke the Greek expeditionary force in its tenth year of fighting against the Trojans, the balance of power suddenly changed and the Trojans started beating the Greeks. For the first time in this long war, they camped in the open, in the expanse between the walled city of Troy and the fortified Greek camp on the beach.  The next day attacked in force and they succeeded in reaching the sandy beach where the Greek ships were stationed. Then they made a fatal strategic error. They tried to burn the ships. 

Sun Tzu says that you always should leave an escape opening for the circled enemy camp. One should press and harass the enemy, but never let it without a potential escape route, because an enemy with its back to the wall or the sea will fight desperately to death. These kind of combats, even if successful, are terribly expensive in terms of fallen soldiers and must be avoided. Hitler, for example, totally encircled the British expeditionary force in the continent, but did not close the trap but let a few kilometers wide opening, allowing them to sail back with their equipment to Britain. That was the classical Chinese and Mongol strategy.

But the Trojans, instead of letting the Greeks embark and row back to where they came from, tried to destroy their only hope of getting away alive from this failed, endless, futile war. The perspective of defeat and slaughter united the Greek fractions, healing their bitter divisions, and hardened their fighting spirit. They beat back the triumphant Trojan forces to behind the high walls and strong gates. The experience of almost-defeat forced them to realize that brute violence would never take Troy. You shall make war with tricks, unheroic but effective. It took ten bloody years for the Greeks to get the idea.