The changdao (simplified Chinese: 长刀; traditional Chinese: 長刀; pinyin: chángdāo; literally: "long knife") was a two-handed, single-edged Chinese sword. The weapon may have developed from the earlier zhanmadao (horse beheading sword). Tang dynasty sources describe the changdao as being identical to the modao (Chinese: 陌刀). This sword was described as having an overall length of seven feet, with a three foot long blade and four foot long grip. This version of the changdao seems to have lost favor after the Tang dynasty. The Taibai Yinjing states:
In one army, there are 12,500 officers and men. Ten thousand men in eight sections bearing peidao; Two thousand five hundred men in two sections with modao.
The term changdao, which simply means "long saber", is also used to refer to a two-handed sword of the Ming dynasty. In modern discussions, the term miaodao, the name of a similar but more recent weapon, is sometimes used to describe these swords. The Japaneseōdachi very much resembles this blade. This weapon was adopted by General Qi Jiguang, who acquired a Kage-ryū (Aizu) manual from Japanese wokou, studied and modified it for his troops and used against enemies on the Mongol border circa 1560. At the time of General Qi it had a specified length of 1.95 meters, similar to the Japanese ōdachi. Its handle was long, apparently slightly more than one-third of its total length, and its curve shallower than that of Japanese swords. Commanding up to 100,000 troops on the Mongol border, General Qi found this weapon so effective that up to forty percent of his commandos had it as a weapon; it stayed in service throughout the late Ming dynasty.
Cheng Zongyou's Martial Arts After Farm Work (1621) contained a manual called Selected methods for the single sword (單刀法選), which described and illustrated techniques for the two-handed sword. According to the manual, the techniques were learned from master Liu Yunfeng, who had studied Japanese fencing.