Treatise on Armament Technology, Volume 39: Strategic Analysis (Tang III)

Shi Siming was a cunning rebel, but it was also because the Tang authority was divided and their commands were not unified that he was able to take advantage of the situation.

The Tang generals had no central authority to report to regarding whether to advance or retreat Because the Tang Emperor feared giving too much power to any one general, he refused to appoint a supreme commander for the nine regional military governors, leading to tactical paralysis. The city of Yecheng held out for a long time without falling, and the cohesion between the officers and soldiers began to disintegrate. Sensing this weakness, Shi Siming led his troops toward the city.

He selected elite cavalry to conduct daily raids beneath the city walls. Whenever the Imperial Army marched out to meet them, the rebels would scatter and retreat to their camps. If the Tang forces prepared for an attack by day, the rebels struck by night; if they prepared by night, the rebels struck by day. Furthermore, Siming frequently dispatched brave men to steal Imperial Army uniforms and insignias original: "裝號" (zhuanghao) – the specific clothing and identification tallies used to distinguish friend from foe. These infiltrators would recklessly slaughter those overseeing the transport of supplies. Wherever people, boats, or carts gathered, the rebels would secretly set fires to burn them. They moved back and forth, gathering and scattering, using their own signals to identify one another, while the Imperial Army remained unable to detect the deception.

Because of these tactics, the various Tang armies ran short of food. Shi Siming then led his main force directly to the city walls to set a date for a decisive battle. The Imperial Army, consisting of six hundred thousand infantry and cavalry, was arrayed north of the Anyang River.

The generals Li Guangbi, Wang Sili, Xu Shuji, and Lu Jiong engaged in the initial combat. The resulting casualties were nearly equal on both sides. Guo Ziyi Often considered the "savior of the Tang," he was a master strategist whose career spanned four emperors followed behind them with his reserves, but before he could finish deploying his formation, a massive gale suddenly arose. It blew sand and uprooted trees, turning the day as dark as night. Visibility was so poor that one could not see a hand's breadth away. Both armies were seized with terror.