It was the surprise attack on Pearl Harbor that finally pushed the United States to enter World War II, but a little-known bombing at the World's Fair in New York City nearly a year-and-a-half before - which resulted in the deaths of two NYPD officers - may have laid the groundwork.
It has been suggested that the bomb may have been planted by a British spy, in an attempt to gain American support for the British cause.
NYPD Lt. Bernard Whalen has studied the World's Fair bombing extensively for two books he wrote on the history of New York's finest.
On July 4, 1940, a bomb went off at the World's Fair in New York City. It has been suggested that the British may have been behind the attack
Two NYPD bomb squad members were killed in the attack and five others were injured
In an interview with the Daily Beast, Whalen refused to point fingers in the unsolved bombing, but said, 'You could draw the conclusion that it was an inside job'.
Exactly a month before the July 4, 1940 bombing, the British evacuated their entire Army from Europe after the Nazis pushed them back to Dunkirk.
That same month, Prime Minister Winston Churchill dispatched Sir William Stephenson to New York City to set up a spy shop for the British intelligence agency, MI6.
One of Stephenson's U.S. spies was Ian Fleming, who went on to author the James Bond novels. And he based the character after World War One hero Stephenson, who he described as 'very tough, very rich, single-minded, patriotic, and a man of few words'.
Joseph Lynch (left) and Ferdinand Socha (right) were the two officers killed in the unsolved bombing
The bomb was found in the British pavilion of the World's Fair. It has been suggested that the British may have been behind the attack to garner American support for WWII
Both Stephenson and Churchill shared the opinion that the British needed the Americans to win the war, so one of his main jobs was turning U.S. public sentiment against the Germans and their allies.
At that point, many Americans were still torn about which side to support, and the British were hardly the only groups maneuvering to win American hearts and minds.
The German American Bund was one group that was spreading the idea of a Aryan state in America with its Long Island retreat where attendees could learn about the Nazi movement.
There was friction between these competing groups as well. Just two weeks before the World's Fair bombing, the German Library of information in the New York City German Consulate building, was bombed, as were the offices of The Daily Worker newspaper, then the outlet of the Community Party. The Soviets at that time had a peace agreement with Hitler.
And just days before the July 4th holiday, the British pavilion at the World's Fair received a phone threat, saying to 'get out of the building. We're going to blow it up'.
In the weeks before the bombing, Winston Churchill