Complex sentence: The clan first distinguished itself during the Jürchen invasion of northern Kyūshū in 1019 and rose to prominence during the Mongol invasion of Japan in 1281, when the heroism of Kikuchi Takefusa helped drive back the enemy.
Split into simpler sentences: The clan first distinguished itself during the Jürchen invasion of northern Kyūshū in 1019. The family rose to prominence during the Mongol invasion of Japan in 1281, when the heroism of Kikuchi Takefusa helped drive back the enemy.