Kobune were the first very useful ships in Rokugan. Methods of curing and treating timber allowed the hulls to last longer. These advancements were made on barges and dugouts. Thus the kobune were born. Later advancements include using pitch to seal the seams between the planks and using seasoned wood to make properly shaped hulls. Most of these advancements were made by the Mantis Clan. Kobune used large rectangular sails with a rigid construction, and some had even three masts. After the 2nd century the kobune became the most common sea vessel in the Empire. Kobune warships featured a quarterdeck for archers at the stern and even the bow.