Complex sentence: The 11th was renamed the 1st Cavalry Division, which had been in South Korea since the Korean War, it became the 2nd Infantry Division and its colors transferred to the 11th Air Assault (Test) at Fort Benning, just before deployment overseas.
Split into simpler sentences: The 11th was renamed the 1st Cavalry Division, which had been in South Korea since the Korean War. The 1st Cavalry Devision's reflagged units became the 2nd Infantry Division and the 1st Cavalry's colors were transferred to the 11th Air Assault (Test) at Fort Benning, just before deployment overseas.