Kafir':

Do not treat the China of 1951 as though it were the China of 1981+.

China truly had a "peasant" army in 1951, with comparatively little artillery, and far less armor than modern formations of equivalent size would deploy.

Their attack achieved the level of success it did because of the poor use of intelligence by decision makers in the region (yes, including MacArthur -- this is one strategic assessment he blew outright; his defense of the Phillipines and insistence upon returning there are arguable, but on this one he simply screwed the pooch), that allowed the Chinese "volunteers" to attack strung out units in poorly developed defense positions. Even so, while pushing us below the 38th parallel, the Chinese lost more than a million men, including many of their best formations. They had, more or less, shot their bolt. On the defensive in the hills of the North, they enjoyed their greatest success, since tactical conditions favored the infiltration/sniping/attrition tactics at which their army was truly experienced.

The US, had they amphib'ed into portions of China that were less rugged, would have held a distinct tactical advantage. Our air support, artillery, and mechanization gave us a huge advantage whenever engagement ranges went up -- as was all too often lacking in the hills/mountains of N. Korea. The Chinese forces were huge, but under-trained and prepared for mechanized warfare.

Strategically, of course, the USA could never have "conquered" China and any tactical success would have, at best, allowed us to remove Chinese support for N Korea. The Communists were adept guerillas of long experience and any effort at occupation that lasted more than a few months would have been painful. Even a limited conventional attack would have been a pricey effort by our standards (to go after China with anything aside from air/naval strikes). What prevented us from seeing this as an option was our concern that the Russians would have gone in -- and they were mechanized and experienced just as were we even if you set aside the possibility of both sides lobbing A-bombs.