Serving in the European Theater of Operations in command of the second platoon of the Anti-Tank Company, 422nd Regiment, 106th Division, during the Battle of the Bulge, December 16–19, 1944, he was wounded and captured.

[7] (Patton reported the raid as the only mistake he made during World War II[8] and General Dwight D. Eisenhower reprimanded him for it.)

Whilst studying for his graduate degree at the University of London (1948–1950) he was employed as a Psychologist at the West Park Hospital, Epsom, Surrey.

[16][3] Over the course of his career Prell pursued long-standing interests in both Edward John Trelawny, a novelist and friend of Percy Bysshe Shelley and Lord Byron, and Pierre Laval, Prime Minister of France in the 1930s and again during the Vichy era.

Both interests arose while living in England in the late 1940s; he discovered Trelawny's relationship to the romantic poets on a holiday to Cornwall, and he befriended René de Chambrun, Laval's son-in-law, in London.

[18] These research materials have been donated to two Southern California libraries: In 1960, Prell married Elizabeth (Bette) Howe, a British novelist[22] and magazine editor.

[24] Donald Prell died on July 28, 2020, at the age of 96, and was interred at the Los Angeles National Cemetery with full military honors.

[25] Prell was posthumously inducted into the U.S. Army's Officer Candidate School Hall of Fame in 2021 for "valorous combat leadership and lifelong service to the nation.

"[26] In December 2022, the Consulate General of France in Los Angeles disclosed that the Legion of Honour medal was authorized for Prell in 2019 for his service to the French Republic during World War II but the award was delayed due to COVID-19.