He was wounded in battle while serving in France during World War I and later played in the National Football League for the Canton Bulldogs in the 1925 NFL season.

In the final game of the season, Army defeated Navy 20 to 0, as Merillat blocked a punt in the end zone for a safety and scored on a 20-yard touchdown pass.

He sailed for France with the American Expeditionary Forces (AEF) in March 1918 and was promoted to the rank of temporary major of the infantry in June 1918.

"[13] When the United States entered the war after the attack on Pearl Harbor, Merrilat resigned from the French Foreign Legion and enlisted in the U.S. Army, where he was given a position training the troops.

Promoted to the rank of colonel, Merrilat was put in charge of the Army's forces at Miami Beach, Florida, during World War II.

Ninety hotels in Miami Beach were taken over by the Army during the war, and Merrilat turned over the keys to the final building to Mayor Herbert Frink in June 1946.

[14] In November 1915, Merrilat became the subject of press coverage when he was sued by Helen Van Ness for breach of promise after breaking off an engagement.