In films of the 1940s and 1950s, Lovejoy mostly played supporting roles. Appearing in movies such as Goodbye, My Fancy (1951) with Joan Crawford, and The Hitch-Hiker (1953) directed by Ida Lupino, Lovejoy was effective playing the movie's everyman in extraordinary situations. He was in several war movies, notably Stanley Kramer's Home of the Brave (1949), Breakthrough (1950), Joseph H. Lewis's Retreat, Hell! (1952) which portrayed the United States Marine Corps' retreat from the Chosin Reservoir (Changjin Reservoir) during the Korean War and as a Marine sergeant again in Beachhead (1954). In 1951, he had the title role in I Was a Communist for the FBI with co-stars Ron Hagerthy, Paul Picerni, and Philip Carey.