Why was the 500,000 elite soldiers of the Ming Dynasty defeated by 30,000 Walla soldiers in Tumubao, while the 202,000-line Ming army defending Beijing was defeated by 100,000 Walla soldiers?

The failure of this civil fortress is entirely due to the headquarters.

The army has no strategic planning at all. With the happy transfer of Wang Zhen, they are not ready for battle at all. Moreover, the heavy rain was the time when morale was low, and they were naturally defeated by Varach. If the morale of the troops on the battlefield is low and they are not prepared for the battle, then the more people there are, the more they become a burden, and the rout of some people will soon turn into the rout of the whole army.

As for Beijing's defense, on the one hand, Valla had no effective means to attack the city, on the other hand, the Ming army was eager to defend its family and its morale was high, coupled with Yu Qian's bravery and reasonable command. In addition, Beijing's defense is not a big break, but Walla can't attack the city, and supplies are not allowed to be besieged for a long time. Finally, the Ming army did not annihilate the main force of Valla.