Firearms are weapons worked by gunpowder. From the fire lance of bamboo, to the gun cast in bronze, to the thick, heavy cannon, it is the same tube, with its material and size changing step by step.
At the siege of De'an in 1132 (Shaoxing 2 of the Southern Song), the defender Chen Gui used bamboo fire lances to burn the enemy's siege equipment, the earliest recorded combat use of the fire lance.
The bronze Xanadu Gun, cast in 1298 (Dade 2 of the Yuan), is the oldest surviving metal-barrelled firearm with a firm date.
At the battle of Ningyuan in 1626 (Tianqi 6 of the Ming), Ming forces used cannon copied from European models, called Hongyi, to repel the Later Jin, and heavy artillery became central to attack and defence.
Firearms Evolution is the class in the chapter on Strategies on firearms. It covers how firearms advanced step by step to the centre of the battlefield, from the bamboo fire lance at the siege of De'an in the Southern Song and the bronze Xanadu Gun of the Yuan to the European-style Hongyi cannon at the battle of Ningyuan in the Ming.