Complex sentence: He was appointed to his first command MASB 16 on 4 November 1940, until 18 November 1940, when he was appointed commander of MASB 18, his final MASB command was MASB 14 which he took up 23 December 1940.
Split into simpler sentences: He was appointed to his first command, MASB 16, on 4 November 1940, which he held until 18 November 1940, when he was appointed commander of MASB 18. His final MASB command was MASB 14, which he took up 23 December 1940.