THE Korean peninsula consists of North Korea and South Korea. They got independence on Aug 15,1945, after which the (erstwhile) Soviet Union entered into Pyongyang on Aug 22, 1945, and the US entered into Seoul on Sept 8 1945. They divided the two countries by drawing 38th Parallel.
These two countries fought war in 1950 and came to armistice in 1953 on the intervention of the US, China and Russia. Since then China is a close ally of North Korea and America is an ally of South Korea. The present disturbance between North Korea and South Korea arose when North Korea tested its third nuclear device this February. In response America and South Korea started a joint military training. Now both sides are using tactics and threatening each other.
In such a deplorable condition China, the strong ally of North Korea, is persuading it not to initiate a war with America and South Korea.
China knows exactly how advance the US military is and how it can easily stopr North Korea from creating a mess in the region. China has an agreement of helping North Korea in time of war. So it will create problems for China to support North Korea against America, which is the biggest market for its commodities.
China has a border of 800 miles with North Korea and if war takes place all refugees will go to China, creating problem for it.
North Korea lacks technology and America will easily crush it. This will create a constant threat for China to have a superpower at its border in North Korea. America already has 29,000 soldiers in South Korea and their number will increase if war takes place, creating a much higher risk for China.
So China, because of its own national interest and sovereignty, is opposing North Korea’s move against Seoul.