 After attending Machinist's Mate "A" School in Great Lakes, Illinois, he served sea tours aboard the and and shore tours at Nuclear Power Training Unit, Windsor, Connecticut, and Radiological Repair Facility in New London, Connecticut.After leaving active duty in 1974, Herdt enlisted in the United States Navy Reserve, serving in various Selected Naval Reserve units while attending Kansas State University.Returning to active duty in 1976, he served as a Naval Reserve Recruiter in Milwaukee, Wisconsin, and in 1978 rejoined the regular navy.