Replace The Beams With Rotten Timbers

Disrupt the enemy's formations, interfere with their methods of operations, change the rules in which they are used to following, go contrary to their standard training. In this way you remove the supporting pillar, the common link that makes a group of men an effective fighting force.

Six Dynasties Period China

    In 383 emperor Fu Jian of Qin, personally led an advance guard of 5,000 horses to attack the Jin general Xie Shi. Discovering that the Jin forces were greater than he anticipated, the emperor had his army form defensive positions along the bank of the river. The Jin armies likewise encamped on the opposite side. Neither side wished to cross first since it was well known that an army is most vulnerable when crossing a river. General Shi sent an envoy across the river with a message that read: " My lord, your army has entered deeply into our territory, and in deploying your ranks you have crowded upon the river. This is the plan for a lengthy stalemate. Do you really want to fight? If you will order your men to withdraw to a safe distance and allow us to cross we can then fight it out and settle the matter quickly." 
    The emperor agreed to the request. When his advisors objected, emperor Fu Jian told them that he planned to turn his army about and attack the Jin after half their troops had crossed. But general Xie anticipated the emperor's treachery and sent scouts disguised as imperial troops to infiltrate the Qin ranks. When the emperor ordered his army to pull back, the disguised Jin troops began to incite panic by spreading the rumor that Qin was withdrawing in defeat and that Jin was in hot pursuit. The retreat quickly turned into a rout as the Qin troops broke formation to escape. The emperor and his generals raced frantically after the fleeing soldiers with whips in hand to stop them, but to no avail. The Jin army quickly crossed the river and pursued the Qin forces inflicting enormous casualties. The emperor was wounded and narrowly escaped. He was captured and strangled a few weeks later.