 According to Stephen Turnbull, the Japanese responded by ordering supplies of iron plates for the building of warships, so that the turtle ship can be "countered in its own terms".According to Hawley, however, the Japanese phrase does not necessarily mean the vessels were covered with iron plates; it could simply refer to the iron spikes protruding from their roofs.In fact, contemporary Korean sources do not support the claim that the turtle ships were ironclad