The seven-year history of the post-war Air Service was essentially a prolonged debate between adherents of airpower and the supporters of the traditional military services about the value of an independent Air Force, spurred by the creation of the Royal Air Force in 1918. On one side were Brig. Gen. Billy Mitchell, Brig. Gen. Benjamin Foulois, a cadre of young former Reserve officers who made up the overwhelming majority of Army pilots, and a few like-minded politicians and newspapers. Opposed were the General Staff of the Army, its senior leadership from World War I, and the Navy. The doctrinal differences were both defined and intensified by struggles for funds caused by the skimpy budgets authorized for the War Department, first by the penurious policies of the Republican administrations in the 1920s, and then by the fiscal realities of the Great Depression. In the end, the struggle for funds as much as any other factor caused the impetus for an independent Air Force.