http://www.centurychina.com/history/faq5.shtml#21
Western sources gave assertions such as "it seems reasonable to assume that China cannot have lost less than half a million men" , "China suffered at least 900,000 casualties", etc. However, such numbers were based on arbitrary estimates which were greatly inflated.
For example, US estimated that in the battle of Chosin reservoir, the Marines air power killed 10,000 Chinese and wounded 5,000, the numbers were artificially high and no evidence could be found to back up these claims. From western combat histories, PVA always cease the fighting at dawn and went to cover, and their white clothing made it very hard to detect even by the Marines at close distance let alone by aircrafts. US estimated that the Marines killed a total of 25,000 PVA troops and wounded 12,500 in the Chosin battle, one has to wonder that if the Marines alone could kill 20% and wound 10% of the entire PVA 9th Army Group, why did the X Corps have to abandon Task Force MacLean and put itself in such a vulnerable situation at the Hungnam beachhead, and then bug out North Korea.
For another example, Van Fleet claimed that UN had inflicted a communist casualty of 234,000 from August to October 1951 during which truce talks were in recess, such an estimate is considered "far too high" by western historians. There are a lot of such cases, when a western historian quoted communist casualty numbers, he had to qualify it with words such as "arbitrary", "far too high", etc.
From the overly inflated numbers, it seems that US generals are not accountable for their battle results, while in PLA, it is a serious misconduct to report false casualty numbers of either side, since such false reports would result in wrong calculations by the nation's leaders. On the US side, American statisticians calculated that in the 8 months ending June 25 1951, PVA suffered a casualty of 600,000 (which would imply that every PVA soldier entered Korea became a casualty), and UN suffered 290,000 (among which 78,800 were American), such gross miscalculations by Washington led to the illusion that US was winning and prolonged the war.
Is that how you explain 1000 years of Korean vassalage to China? You think we were nice to you and didn't demand our protection money? Looks like the delusions of some little pea-sized country is being shattered.
