attack. Shooting from the back of a moving horse may be more accurate if the arrow is loosed in the phase of the gallop when all four of the horse's feet are off the ground. The Mongols may have also used crossbows (possibly acquired from the Chinese), also both for infantry and cavalry, but these were scarcely ever seen or used in battle. The Manchus forbade archery by their Mongol subjects, and the Mongolian bowmaking tradition was lost during the Qing Dynasty. The present bowmaking tradition emerged after independence in 1921 and is based on Manchu types of bow, somewhat different from the bows known to have been used by the Mongol empire. Mounted archery had fallen into disuse and has been revived only in the 21st century. Sword Mongol swords were slightly curved Turko-Mongol sabers, which they used for slashing attacks but could also use to cut and thrust, due to its shape and construction. This made it easier to use from horseback. Warriors could use the sword with a one-handed or two-handed grip. Its blade was usually around in length, with an overall length of approximately . Gunpowder Jin dynasty The first concerted Mongol invasion of Jin occurred in 1211 and total conquest was not accomplished until 1234. In 1232 the Mongols besieged the Jin capital of Kaifeng and deployed gunpowder weapons along with other more conventional siege techniques such as building stockades, watchtowers, trenches, guardhouses, and forcing Chinese captives to haul supplies and fill moats. Jin scholar Liu Qi (劉祈) recounts in his memoir, "the attack against the city walls grew increasingly intense, and bombs rained down as [the enemy] advanced." The Jin defenders also deployed gunpowder bombs as well as fire arrows (huo jian 火箭) launched using a type of early solid-propellant rocket. Of the bombs, Liu Qi writes, "From within the walls the defenders responded with a gunpowder bomb called the heaven-shaking-thunder bomb (震天雷). Whenever the [Mongol] troops encountered one, several men at a time would be turned into ashes." A more fact based and clear description of the bomb exists in the History of Jin: "The heaven-shaking-thunder bomb is an iron vessel filled with gunpowder. When lighted with fire and shot off, it goes off like a crash of thunder that can be heard for a hundred li [thirty miles], burning an expanse of land more than half a mu [所爇圍半畝之上, a mu is