The World War II was a defining period in modern history, as the outcome of the war strongly affected most nations of the world, even after it ended. The US initially did not seek active military intervention but the attack on Pearl Harbor eventually led it to enter into War against the Axis nations.
The US had largely taken an isolationist stance as the war began in Europe. The American people and leadership, for the most part, saw it as Europe’s problem, but as the situation grew dire several factors led the United States to consider intervention at one point or the other. The Pearl Harbor attack became the decisive moment for the US to finally make that decision. Japan had allied with the fascist government in Italy and Nazi Germany in 1940 to forge a Tripartite Pact, in which all three were to support each other and work towards a new world order. Together with Japan, Italy and Germany declared war against the United States in December 1941 (JDF78).
The decision to not join the war until the US was actively attacked was largely a wise one. The turmoil left by World War 1 was still far from over and public sentiments according to a poll in 1939, were still against Intervention (94%), while the military force was still not ready (Loproto). It was only about 100,000 men strong against millions of Germans and it would not have made much difference, had they joined earlier. Therefore, were America to enter earlier, it may have led to a total decimation of the American forces.
From an economic point of view, the war did not pose a threat to the US economically, and joining the war earlier would have only threatened a weak economy. Furthermore, by not participating actively, the US benefitted economically by manufacturing and selling vehicles and military equipment for the Allies. There were no formal defense alliances with Britain or France that obligated the US to attack. So as Pearl Harbor was attacked and the US began to actually see its control over the Pacific diminish, the people too had forgotten about the economy and public perceptions began to change. In that sense, it was by large a wiser decision to join in the war, only when it had become absolutely necessary.
JDF78. Reasons for American Entry Into WWII. 30 April 2017. 29 March 2018.
Loproto, Mark. Why Didn’t America Join the War Sooner? 19 January 2017. 29 March 2018. <https://visitpearlharbor.org/didnt-american-initially-join-war/>.