The Mongol bow is a recurved composite bow renowned for its military effectiveness. The old Mongolian bows that were used during the times of Genghis Khan were smaller than the modern weapons used at most Naadam festivals today. Modern Mongolian bows are larger and have string bridges. The modern design is very similar to the Manchurian bows used by the Chinese military during the Qing Dynasty. Ancient and modern Mongol bows are part of the Asian composite bow tradition. The core is wooden, with horn on the belly (facing towards the archer) and sinew on the back, bound together with animal glue. As animal glue is dissolved by water, composite bows may be ruined by rain or excess humidity; a wrapper of (waterproof) birch bark may give limited protection from moisture and from mechanical damage. The bow is usually stored in a leather case for protection when not in use.