sentences:  After the Chinese Civil War had broken out in full scale on June 22, 1946, the communists had many difficulties.Zhangjiakou, the capital of the communist base in border area of Shanxi-Chahar-Hebei was sandwiched between nationalist strongholds both in the east and the west.The nationalist stronghold Datong in the west was guarded by the nationalist 38th Division, the 5th Cavalry Division, the 6th Cavalry Division and some local security forces totaling 20,000.