What was the cause of the Korean War?

Without China's knowledge, North Korea launched a long-planned war with Stalin's permission. Why didn't you inform China in advance? What does this mean? The simplest interpretation is to worry that China doesn't agree or doesn't trust China at all! I prefer the latter, because the new China has no weight at all, and China still owes North Korea a favor at that time. To put it bluntly, North Korea regards us as poor relatives. Is it necessary to discuss something with you? Don't let it out again! The rulers wanted to be a great man, and their heads were almost 100 degrees, but Stalin was very calm. Didn't Stalin know that the United States would send troops? No, he must know. This is Stalin's insidious place. He wants to control the northeast of China, which is justified! North Korea is bound to fail. If China didn't send troops, Stalin would have an excuse to station troops in the northeast. If China is defeated, he also has an excuse to send troops to the Northeast. This is a reasonable explanation for the Soviet Union's delay in sending air support. But he didn't count that the volunteers forced the American army back to the 38th parallel, and the United States was not a fool and didn't want to be used by Stalin. After the allied forces retaken Seoul, they did not launch a large-scale attack, but adopted a conservative position. Only when Han Jun didn't understand, did he raid the White Tiger Regiment. To sum up, the cause of the Korean War was Stalin's conspiracy! China's invasion was absolutely correct! ! !