Moreover, there was talk among the U.N. commanders—notably MacArthur—about a potential campaign against the People's Republic of China. In an effort to dissuade UN forces from completely overrunning North Korea, the People's Republic of China issued diplomatic warnings that they would use force to protect North Korea, but these warnings were not taken seriously for a number of reasons, among them the fact that China lacked air cover to conduct such an attack. This changed abruptly on 19 October 1950, when the first of an eventual total of soldiers under the command of General Peng Dehuai crossed into North Korea, launching a full-scale assault against advancing U.N. troops. The PRC offensive caught the UN completely by surprise; UN forces realized they would have to fall back, and quickly executed an emergency retreat. UN assets were shuffled in order to cover this retreat, and as part of the force tasked with covering the UN retreat "Missouri" was moved into Hungnam on 23 December to provide gunfire support about the Hungnam defense perimeter until the last UN troops, the U.S. 3rd Infantry Division, were evacuated by way of the sea on 24 December 1950.