a fitting described for the first time three weeks earlier in Yi Sun-sin's diary. Stephen Turnbull, however, points out the fact that in February 1593 the Japanese government ordered the military to use an iron plate in building ships, possibly in response to the Korean attacks. There are no contemporary Korean sources from Yi Sun-sin's time that refer to the turtle ship as ironclad. Admiral Yi Sun-sin himself makes no mention of such a design in his comprehensive war diary. His nephew Yi Beon, who also witnessed the war and left a historical account of the events, do not mention iron cladding either. The annals of King Seonjo, a many thousand pages long compilation of all kinds of official documents of the period, are also silent on the subject. Prime Minister Ryu Seong-ryong even explicitly described the turtle ship as "covered by wooden planks on top". There is also the question of motivation for adding metal plating. Since the Japanese did not commonly employ cannons on their ships until decades later, let alone use plunging cannon fire, any plating would have logically been designed as an anti-incendiary measure, not to withstand cannonballs. The Japanese did commonly use fire arrows and a form of exploding grenades called in naval battles during this period. As it was, Yi Sun-Sin, who was largely cut off from government supplies throughout his campaigns, found the small amount of fifty pounds of iron worth mentioning in his war diary. Therefore, Hawley believes that it is unlikely that Admiral Yi would have passed in silence over the estimated six tons (twelve thousand pounds) of iron necessary for even a single outfit. Such a large amount of iron was equivalent to one ship's entire ordnance and would have probably been considered more helpful in casting additional cannons, mainly since the Koreans were well aware that Japanese warships were practically devoid of naval guns. Confronted with a Japanese enemy who relied on small arms fire and boarding tactics, and faced by the logistical and financial difficulties involved in acquiring such a large amount of iron, any iron cladding of the Korean vessels have been deemed by Hawley inherently superfluous: Evidence for an iron-plated turtle ship is found, according to Stephen Turnbull, in a 1795 drawing of the turtle ship where the shell is shown as being covered by a distinct hexagonal pattern, implying that something is covering the wood