Complex sentence: Jax is clear-headed, careful and always keeping a watch on what his men are doing, but when the need arises, he is a beast on the battlefield with the attitude and ferocity of a lion.
Split into simpler sentences: Jax is clear-headed, careful, and always keeping a watch on what his men are doing. When the need arises, he is a beast on the battlefield with the attitude and ferocity of a lion.