With the arrival of the Race's Conquest Fleet in 1942, the completion of an Americanatomic bomb became that much more important. Thus, the pressure was on for Leslie Groves to see the project to completion. He accepted a sample of plutonium from a Britishsubmarine in Boston Harbor. He carried the plutonium to Denver, where he turned it over to the US physicists working on an atomic bomb. Groves remained in Denver as commander of the Manhattan Project until that project's completion. He designed the defenses of Denver when the Race advanced on that city in 1944. Those defenses were implemented by Omar Bradley. Groves oversaw the Battle of Denver alongside Bradley.