"In 1948, as the Communists switched to conventional, but mobile, operations, the Nationalist forces in Manchuria were isolated and then destroyed, and the Communists regained Shensi and conquered much of China north of the Yellow River. Communist victory in Manchuria led to a crucial shift in advantage, and was followed by the rapid collapse of the Nationalists the following year. The Communists made major gains of matérial in Manchuria, and it also served as a base for raising supplies for operations elsewhere. After overrunning Manchuria, the Communists focused on the large Nationalist concentration in the Suchow-Kaifeng region. In the Huai Hai campaign, beginning on 6 November 1948, each side committed about 600,000 men. The Nationalists suffered from poor generalship, including insufficient coordination of units, and inadequate use of air support, and were also hit by defections. An important factor in many civil wars, defections from the Nationalists proved highly significant in the latter stages of the Chinese Civil War. Much of the Nationalist force was encircled thanks to effective Communist envelopment methods, and, in December 1948 and January 1949, it collapsed due to defections and combat losses."