Complex sentence: The allies turned all their guns, and the guns in the two Chinese forts they had captured, on these two forts, blew up another powder magazine in one, and shortly the Chinese soldiers abandoned the forts.
Split into simpler sentences: The Allies turned all their guns, and the guns in the two Chinese forts they had captured, on these two forts. They blew up another powder magazine in one, and shortly afterwards the Chinese soldiers abandoned the forts.