Complex sentence: In 1909 he retired from the army with a rank of a lieutenant colonel, and later that same year he was invited by Theodore Roosevelt to accompany the Smithsonian-Roosevelt African Expedition as naturalist.
Split into simpler sentences: In 1909 he retired from the army with a rank of a lieutenant colonel. Later that same year he was invited by Theodore Roosevelt to accompany the Smithsonian-Roosevelt African Expedition as naturalist.