Yisun Shin's Secret Weapon

Admiral yisun shin and his shipwrights built specially made warships designed specifically to counter the japanese weapons. They were heavily armed gunboats equipped with rows of heavy cannons on either side, and the top was completely covered by a heavy wooden roof,. curved like a turtle shell and bristling with hundreds of iron spikes. On the prow, there was a huge agon's head carved from wood, and a cannon could be fired from within its mouth. Korean warships were already pretty good, but this thing is like a tank. The turtle ships work like a charm. Over the next several weeks, hundreds of broken Japans are left littering the korean coast.