Complex sentence: In 280, when forces of the Jin dynasty invaded Wu, Yu Zhong joined the brothers Lu Yan and Lu Jing in defending Wu and they were all killed in action, after which Wu was conquered by Jin.
Split into simpler sentences: In 280, when forces of the Jin dynasty invaded Wu, Yu Zhong joined the brothers Lu Yan and Lu Jing in defending Wu. They were all killed in battle, after which Wu was conquered by Jin.