the northeast specialized in long spears. After the Han dynasty, the crossbow gradually faded in importance until it made a mild resurgence during the Tang dynasty, under which the ideal expeditionary army of 20,000 included 2,200 archers and 2,000 crossbowmen. References to "great shields" occur in their usage on the front line to protect spearmen and crossbowmen. Shields were also commonly paired with the single edged dao and used among cavalrymen. Descriptions of the Battle of Guandu mention that Cao Cao's soldiers employed shield cover above their heads each time they moved out into the open due to oppressive arrow fire from Yuan Shao's wooden towers. Although Zhuge Liang is often credited with the invention of the repeating crossbow, this is actually due to a mistranslation confusing it with the multiple bolt crossbow. The source actually says Zhuge invented a multiple bolt crossbow that could shoot ten iron bolts simultaneously, each 20 cm long. Dark armour A report in 231 AD mentions the capture of 5,000 suits of "dark armour" (xuan kai or xuan jia 玄鎧/玄甲) and 3,100 crossbows. Dark armour appears in Han texts as well, but only as the attire worn by honor guards at funeral processions. The only known trait about dark armour is that it reflected the sun's rays. This probably means dark armour was made of high quality steel, which was often associated with black ferrous material. Brilliant armour Cao Zhi mentioned three different kinds of armour, two of which were variants of "brilliant" armour: Brilliant armour was made of decarburized steel, which shines blue-black when polished, giving it its name. Chen Lin described brilliant armour in the following manner: Wheel catapult Ma Jun, a military engineer serving under Cao Wei, devised a siege weapon which threw large stones using a wheel. This device consisted of a drum wheel attached with a curved knife. When rotated, the stones which hung on the wheel would be cut loose by the knife and launched. It is not clear how well this device worked in practice. Successful tests with roof tiles instead of stones are mentioned, but according to Liang Jieming, this contraption never made it past the testing phase and could not have been possible with the technology available at the time. Special weapons The historical novel Romance of the Three Kingdoms attributes a number of fictional weapons, often with special names, to certain individuals. Examples include