 In fact, the Jin military's use of cannons, grenades, and even rockets to defend besieged Kaifeng against the Mongols in 1233 is considered the first ever battle in human history in which gunpowder was used effectively, even though it failed to prevent the eventual Jin defeat.On the other hand, the Jin military was not particularly good at naval warfare.Both in 1129–30 and in 1161 Jin forces were defeated by the Southern Song navies when trying to cross the Yangzi River into the core Southern Song territory (see Battle of Tangdao and Battle of Caishi), even though for the latter campaign the Jin had equipped a large navy of their own, using Han Chinese shipbuilders and even Han Chinese captains who had defected from the Southern Song.