Complex sentence: The motivation arose during the Second World War when the United States Public Health Service and the Selective service embarked upon a large scale project to weed out all syphilitic men called up for induction.
Split into simpler sentences: The motivation arose during the Second World War when the United States Public Health Service and the Selective service embarked upon a large scale project. The objective was to weed out all syphilitic men called up for induction.