Complex sentence: While engaging in the battle, he was promoted three different times, starting with First Lieutenant, at the beginning of strategic talks, Captain in 1864, while actively fighting, and near the conclusion of the battle, Brevet Major General.
Split into simpler sentences: While engaging in the battle, he was promoted three different times. He was promoted to the rank of first lieutenant in 1863, and Captain a year later; and near the conclusion of the battle, Brevet Major General.