100,000 Tang Taejong's army was stronger than 1.13 million Suyangje'

The Sui and Tang invaded Goguryeo, but eventually they were not successful... but the Tang invasion was more successful and threatening to Goguryeo than the Sui invasion... The Sun Dynasty invaded Goguryeo with a huge army of 1.13 million troops, but not only failed to capture Yodongseong Fortress, but Tang Taejong, who invaded with a small number of 100,000 troops, captured Yodongseong Fortress and most of Yoseo Province.In the end, the last one can't fall in the Battle of Ansi and retreat...Rather than losing the battle, it was a war in which the Tang army collapsed on its own due to infectious diseases and climate...In fact, the early advance of the Tang army to Goguryeo was so successful that the Malgal people, who were loyal to Goguryeo during the invasion of the Tang Dynasty, betrayed Goguryeo and cooperated with the Tang Dynasty. Why was it easy to accomplish with less than one-tenth of what you couldn't do with a huge number of 1.13 million?   The fact that the 1.13 million troops of the Sui Dynasty were large numbers, far from elite troops, and that 100,000 troops of Tang were selected mainly from the Tang army is not unusual in ancient war history. The hundreds of thousands of troops that appear in Chinese history seem to be a great force if you think about it vaguely, but I think the power varies greatly depending on how they are organized...A million units randomly drawn from 10 to 50s, and a hundred thousand units selected mainly by young soldiers, may seem stronger at first glance, but in reality, the elite 100,000 units are stronger.

The lesson we can see here is that a large army, which has only a large scale of overall war capabilities, has a blind spot. In particular, the prolonged food supply line also becomes serious. Moreover, Goguryeo's counterattack small-scale tactics mainly aimed at destroying food supply ships and serve as a basis for victory or defeat. And crucially, in the case of the Sui Dynasty, the unstable political situation within the home country would have also contributed to the decline in the ability to carry out the war.