Complex sentence: He continued to advance within the army: being promoted Lieutenant-Colonel in 1898, named colonel in 1903 and regimental commander of the 35th Artillery Regiment (35e R.A) at Vannes.
Split into simpler sentences: He continued to advance within the army: being promoted Lieutenant-Colonel in 1898, and colonel in 1903. As a colonel he became regimental commander of the 35th Artillery Regiment (35e R.A) at Vannes.