Complex sentence: He was promoted to become a Colonel in 1903, then Brigadier General (Général de Brigade) in 1907, returning to the Staff College as Commandant from 1907--1911.
Split into simpler sentences: He was promoted to become a Colonel in 1903. Then Brigadier General (Général de Brigade) in 1907, returning to the Staff College as Commandant from 1907--1911.