Complex sentence: In addition to the units listed above and with manpower possibly drawn from some of them a Mountain Rescue Team was based at West Freugh from 1945 to 1956 when the MRT at RAF Leuchars assumed responsibility for the area covered by West Freugh.
Split into simpler sentences: In addition to the units listed above (and with manpower possibly drawn from some of them) a Mountain Rescue Team was based at West Freugh from 1945 to 1956. After 1956 the MRT at RAF Leuchars assumed responsibility for the area covered by West Freugh.