The reasons behind China’s strong support of North Korea include historical reasons as well as military strategic considerations despite the fact that North Korea does not seem to be cooperative to join the six-party talks proposed by China.
Historical factor: The Korea War
First, China abides by its commitments. China attaches importance to Sino-DPRK friendship which was created in blood with lives sacrificed. On June 26, 1950, North Korea launched a sudden war against South Korea, its army moved all the way to Busan driving the U.S. and South Korean troops almost off the sea. However, the good environment was not durable as the Korean People’s Army increasingly presented weakness, when U.S. forces carried out the Inchon landing, the war situation was reversed, the U.S. military will soon hit the North Korea border. At the time of imminent destruction of North Korea, the Chinese People’s volunteers army decided to enter into war, and fought the US-led forces back to the south of the military demarcation line. The current Chinese leaders still cherish the friendship mainly created in this historical event. Two parties only get together truly when they go through difficulties.
Ecological factor: Socialism
North Korea and China both adopt socialism. Difference is China develops through approaching market economy while North Korea resists a free market. Anyhow, the shared ecological understanding keeps the two countries together despite some political conflicts.
Military strategic considerations: North Korea to act as buffer area between US and China
Third, China wants North Korea to act as buffer area between US and China to avoid direct confrontation with US troops although North Korea is small. Thus, even there is costs for China to support North Korea, it is worthy from a strategic and military perspective. For the similar consideration, some believe that Mongolia’s plan to rejoin China was declined because it could act as buffer area between China and Russia.