Complex sentence: When the Allies invaded French North Africa in 1942, Darlan was the highest-ranking officer there, and a deal was made, giving him control of North African French forces in exchange for joining their side.
Split into simpler sentences: When the Allies invaded French North Africa in 1942, Darlan was the highest-ranking officer there. The allies made a deal with him, giving him control of North African French forces in exchange for joining their side.