Or the new Chinese. Someone here talked about the underperformance of the Americans versus the Chinese in the winter of 1950/51 and a underestimation of the enemy factored into that. Back in the 1940s, if you went up to a American military man and said "Chinese military effectiveness" he would have assumed you were revealing the punchline to a joke. And the Chinese military had been a joke for the past century, earning itself global derision and a near uninterrupted string of embarrassing defeats. When MacArthur during the Korean War dismissed the prospect of Chinese intervention with the line "If they cross the Yalu I will make of them the greatest slaughter the world has ever known," he was speaking based on his personal experience with the armies of Chinese warlords. Unfortunately, since the China experts were in the process of being purged by rabid anti-communists who blamed them for "losing China" there was no one to tell him that the Chinese communists would be a very different beast indeed (although given it's MacArthur we're talking about, he probably wouldn't have believed them).