In China, heavy cavalry was developed during the Han dynasty (202 BC–220 AD), with armoured lancers becoming widespread during the Western Han era. Armoured cavalry, with both soldier and steed clad in complete armour, were employed in the late Han dynasty, and became widespread in the 4th century AD, where it was the main striking force of the armies of the Northern dynasties of China (4th century to 6th century.) During the Tang dynasty (618 to 907) the importance of infantry and lighter-armed cavalry and infantry increased while that of the armoured cavalry decreased, with horse armour seldom used. However, armoured cavalry were again used by the Song dynasty (960–1279) and its enemies, including the Jin, Xi Xia, Mongols, and Khitans.