The People's Republic of China is no longer an ally to North Korea. The alliance ended soon after the conclusion of the Korean War.
Because China is North Korea's ally.
It means North Korea is capable of becoming a powerful ally to China in any possible war.
Nationalist China was a US ally. Red China entered the war.
Korea's primary ally was China, who supplied weapons and soldiers to the Korean Army during a majority of the Korean War. Many would agree that the Soviet Union was also an ally to North Korea, but China certainly made more of an impact.
North Korea was communist. Red China entered the later in 1950, becoming an ally to North Korea.
North Korea has a number of allies; the most prominent is China. North Korea is also allied with some Middle Eastern nations, having sold missiles to Iran and Syria, for example.
Communist China and North Koreacommunist china and North Korea
China would much prefer not to have to side with either the US, a major trading partner (and debtor to China) or North Korea, an ideological ally from the Cold War era. I believe that China will do whatever it can to remain neutral in any conflict that may arise between the US and North Korea. Of course, China is not entirely predictable, and they may fool me.
North Korea is bordered by China and Russia to the north.
China would prefer a nuclear-weapon-free Korean peninsula. However, China is North Korea's foremost foreign ally, so it is often unwilling to join the US and other nations in boycotting or sanctioning North Korean unwillingness to forego nuclear weapons.
China, North Korea, and South Korea are all different countries.
China still regards itself as an ally of North Korea; they both claim to be communist states, although the claim is not that convincing in either case (China has embraced capitalism, and North Korea is just a despotic monarchy ruled by the Kim dynasty) however, China has also asked North Korea to show restraint and to refrain from going to war, therefore, it seems that if North Korea does go to war at this time (2013) it will have no allies. They will be on their own.