Complex sentence: In March 1942, Hitler issued Directive 40, requiring that an invasion force be defeated before it could land or on the coast; in November 1943, Hitler added Directive 51, for the reinforcement of the defences of Western Europe.
Split into simpler sentences: In March 1942, Hitler issued Directive 40, requiring that an invasion force be defeated either before it could land or on the coast. In November 1943 Hitler added Directive 51, requiring the reinforcement of the defences of Western Europe.