Wendt attended the Naval Postgraduate School from June to September 1939, for instruction in applied communications, but the course was cut short when President Franklin D. Roosevelt instituted Neutrality Patrol operations, in which he was engaged as gunnery officer and first lieutenant aboard the destroyer in the Panama Canal Zone until June 1940. He then served six months as training officer on the staff of Commander Destroyer Squadron 27 before being transferred in December to the staff of Commander Destroyer Squadron 30 until September 1943, for duty conducting escort of convoy operations and participating in the invasion of North Africa.