Born in New York City, Lovett first fell in with the local Irish gangs around the Brooklyn waterfront as a teenager. The day after America's entry into World War I, Lovett enlisted in the United States Army. He was assigned to Company C, 13th Machine Gun Battalion, 77th Infantry Division. During fierce combat on the Western Front, Lovett was awarded the Distinguished Service Cross for bravery. Upon his return to Brooklyn, he resumed his place as head of the Jay Street Gang, a group of toughs who sparred with Dinny Meehan's rival White Hand Gang for control of Brooklyn's lucrative waterfront rackets.