Massed-chariot warfare became all but obsolete after the Warring-States Period (476–221 BC). The main reasons were increased use of the crossbow, use of long halberds up to 18 feet long and pikes up to 22 feet long, and the adoption of standard cavalry units, and the adaptation of mounted archery from nomadic cavalry, which were more effective. Chariots would continue to serve as command posts for officers during the Qin dynasty (221–206 BC) and the Han Dynasty (206 BC-220 AD), while armored chariots were also used during the Han Dynasty against the Xiongnu Confederation in the Han–Xiongnu War (133 BC to 89 AD), specifically at the Battle of Mobei (119 BC).