Complex sentence: Although he was recommended for the command of a division, after organising the Auxiliary Units, a Stay-behind force which would act against a German invasion of Britain, Gubbins rejoined MI (R) and in 1943 became the Director of the Special Operations Executive.
Split into simpler sentences: Although he was recommended for the command of a division, he was appointed to organise the Auxiliary Units, a Stay-behind force which would act against a German invasion of Britain. Gubbins later rejoined MI (R) and in 1943 became the Director of the Special Operations Executive.