Lao Liang: Why did the Japanese invade more than half of China and come to Shanxi?

Your understanding is wrong. Shanxi was occupied by Japan during its invasion of China. It was Tongguan-Three Gorges Line that trapped the Japanese army. It has never been able to enter southwest and northwest.

There are two reasons. First, the desperate China soldiers and civilians fought bravely under the banner of the national war of resistance. Take the Kuomintang army as an example. At the same time, they must defend Chongqing and the home front to the death. Second, the Japanese army is extremely vicious, the front is too long, and the soldiers are not prepared for the war.