Widdecke received the Navy Cross, the United States military's second-highest decoration awarded for valor in combat, for his actions during the Recapture of Guam in July 1944.

He attended high school in Dallas in 1937 and then graduated from the University of Texas at Austin in June 1941 with a Bachelor of Arts degree.

[1] With the activation of 22nd Marine Regiment under Colonel John T. Walker, Widdecke was promoted to the rank of first lieutenant and appointed commander of Headquarters Company of 1st Battalion.

Widdecke and his men secured a position on the beach in the face of strong opposition and prepared for the attack against the fanatic Japanese holding Orote Peninsula and its strategic airfield.

He served under Major General William T. Clement until February 1948, when he was sent to Quantico to attend the Junior Course at Marine Corps School.

[1] On completing the course in August 1948, he sailed for Guam, where he was appointed assistant chief of staff for personnel within 1st Provisional Marine Brigade under Brigadier General Edward A. Craig.

[4] In June 1950, Widdecke was ordered back to the United States and appointed an instructor in the Tactical Operations Group, Marine Corps Educational Center, at Quantico.

He was then ordered to Panama and spent the next three years as head of the military assistance, plans and policy, Joint Staff of United States Southern Command under General Andrew P. O'Meara.

[1] In August 1965, Widdecke assumed command of the 5th Marine Regiment at Camp Pendleton and supervised its deployment to Okinawa, Japan in early 1966.

[5] He later acted as chief of staff, Task Force X-Ray under Brigadier General William A. Stiles in the Chu Lai area and took part in combat with Vietcong and North Vietnamese troops.

[1] Widdecke was posted to Honolulu, Hawaii, and appointed chief of staff, Fleet Marine Force, Pacific under Lieutenant General Victor H. Krulak.

[1][3] However Widdecke was ordered back to Vietnam in April 1970, when the commander of 1st Marine Division, Edwin B. Wheeler, suffered serious injuries in a helicopter crash.

[6] Widdecke oversaw Operation Imperial Lake during September of that year with the task of destroying North Vietnamese troops in Que Son.

Following the operations in Quảng Nam Province in the fall-winter period of 1970, Widdecke began preparing 1st Marine Division for redeployment to the United States.