According to historian Walter LaFeber, Truman was known to approach defense budgetary requests in the abstract, without regard to defense response requirements in the event of conflicts with potential enemies. Truman would begin by subtracting from total receipts the amount needed for domestic needs and recurrent operating costs, with any surplus going to the defense budget for that year. From the beginning, Johnson and Truman assumed that the United States' monopoly on the atomic bomb was adequate protection against any and all external threats. Johnson's unwillingness to budget conventional readiness needs for the Army, Navy, or Marine Corps soon caused fierce controversies within the upper ranks of the armed forces. From fiscal year 1948 onwards, the defense department budget was capped at the amount set in FY 1947 ($14.4 billion), and was progressively reduced in succeeding fiscal years until January 1950, when it was reduced yet again to US $13.5 billion.