Complex sentence: Commissioned on 31 January 1942, "U- 217" served with 9th U-boat Flotilla from 1 August 1942 until she was sunk.
Split into simpler sentences: Commissioned on 31 January 1942, "U- 217" served with 9. Unterseebootsflottille (U-Boat Flotilla) from 1 August 1942 until she was sunk.