China's patience wearing thin with erstwhile ally North Korea

Six decades after treating traumatised Chinese soldiers from the battlefields of Korea, psychiatrist Xue Chongcheng remains convinced their sacrifices - that forged bonds between Beijing and Pyongyang in blood and fire - were essential.

But the ties are tarnishing under the passage of time and generational change, with China rising to the forefront of global economics and geopolitics while frustration grows with a frequently troublesome nuclear neighbour, say analysts and ordinary Chinese.

China sent hundreds of thousands of soldiers to the Korean peninsula, the infamous "human waves" that turned the tide early in the 1950-53 conflict, sending United Nations forces led by US General Douglas MacArthur retreating southward after they had pushed invading North Korean troops almost back to the Chinese border.

Historians debate the number of Chinese dead. Western estimates cite 400,000, while Chinese sources appear to have settled in recent years on a toll of about 180,000.

Whatever the true figure, the war, which ended in a truce on July 27, 1953, has for decades had a special place in modern Chinese history and identity.

It began less than a year after Mao Zedong and the Communist Party finally won China's cataclysmic civil war and established the People's Republic in 1949.