Warren was born on December 12, 1918, in Milwaukee, Wisconsin. His father was a first-generation American of Danish heritage, and his mother was a native of Sweden. The family resided on a small farm in Kimberly, Wisconsin, where Warren received his elementary education in a two-room schoolhouse. Later, they relocated to Aitkin, Minnesota, where the family continued their agricultural pursuits.
Warren was a gifted athlete, demonstrating proficiency in boxing, ice skating, and the javelin throw. His passion, however, was baseball, where his height of six feet and weight of 175 pounds made him an exceptional pitcher.
Following high school, Warren served with the Civilian Conservation Corps and also enlisted in the National Guard as an artilleryman, with deployments in Alabama and California. To meet the prerequisite for flying school, he attended Gustavus Adolphus College in St. Paul, Minnesota, completing two years of study. Driven by his aspiration to fly, Warren enlisted in the Army Air Corps as an aviation cadet on October 19, 1941. His basic training took place at Lemoore, California, followed by advanced training at Luke Field, Arizona, where he graduated with Class 42-E in May 1942. Notably, Christensen was one of four pilots from the 118th (along with Cox, Davis, and Eley) who remained together from Basic Flying School in March 1942 through their deployment to the China-Burma-India (CBI) theater. In India, Christensen was assigned to 'A Flight' and served as the assistant flight leader.
On June 12, 1944, the 118th received orders to depart Chabua, India, en route to Kunming, China. The pilots were tasked with ferrying their P-40 aircraft over the treacherous Himalayan "Hump." Approximately 180 miles into the flight, Christensen encountered an issue with his oxygen supply. He communicated with McComas via radio, stating his intention to return to Chabua. Tragically, Christensen never reached his destination and is officially listed as Missing in Action (MIA).
MACR 5810