It was only after WW II that the U.S. reversed its longstanding policy of isolationism. Yet since the consolidation of its borders following the Revolutionary War, the U.S. announced it would not engage in any foreign affairs, nor permit Europe’s interference in the New World. That Monroe Doctrine, as it came to be called, kept the United States on the sidelines during the start of WW I. The Doctrine still prevailed at the start of WW II, although this time there would be some exceptions.

On this day, November 13, in 1941, three weeks before the attack on Pearl Harbor would bring the U.S. in military force, Congress amended The 1935 Neutrality Act to allow critically-needed supplies to reach Europe.

In keeping with the country’s official policy, the Neutrality Act forbade the sale of weapons of ammunition to warring states. The act was beefed up even more two years later with the provision allowing the president to keep ships from entering war zones. But as Hitler overran Poland and France and began preparations to face down Britain, the White House understood they had to take a side.