Why Did The United States Adopt Internationalism After World War I?

What was, in your opinion the most important factor that led the United States to abandon its policy of isolationism and adopt internationalism after Second World War?
When the second world war ended, US got stuck in such a network of alliances and signing of international organizations that her retirement to her continent and adopting the policy of isolationism become quite impossible for her. But the most outstanding reason, that drew out her out from her isolation was, the rise of her potential rival, USSR. USSR had adopted the policy of communism through which it wanted to upset the world order and was adamant to communize the whole world. Therefore to contain it, there was no capable power in sight, as the war had ravaged the rest of powerful states to such an extent that they were not even able to feed their people. In that case of scenario, US abandoned her policy of isolationism and entered the world politics to neutralize the red menace.
After the Second World War, when the treaty of Versailles was signed and Europe had got the sigh of relief, US seemed no reason to entangle herself anymore in the European
affairs. Therefore she preferred to remain aloof from European politics for the time being, until another threat to peace arises. But the US remained in her shell for about twenty one years. Though, the Second World War had broken-out in in Europe in 1939, it preferred to remain aloof from it.
The US had to abandon her policy of isolationism when the imperialist Japan appeared on the scene. Because of her smaller land area and deficiency of raw materials, she was compelled to acquire colonies and draw raw materials and men power from them. So she attacked the Chinese Manchuria. As expected, she ended up USSR and USA to turn monstrous. The former because it had casted its covetous eyes on Manchuria, while the latter, because it knew that Japan is not going to remain content on mere possession of Manchuria, it will for sure, put the US east Asian possessions in jeopardy. Therefore US put oil embargo on japan. Without oil, Japan’s industry would not function. So it was left with one choice, i.e. to invade oil rich British Malaya.
The only thing which deterred japan to invade Malaya was the US military base in the pacific, the Pearl Harbor. If japan wants to colonize the British Malaya, Pearl Harbor has to be destroyed. So japan planned to undergo a clandestine attack on Pearl Harbor. On December 7, 1941, without any warning, Japan attacked pearl harbor leaving about 2,500 dead. Now the US had no option but to enter the war. The US entry into the war swung the needle of the war in allies’ favor. With its vast resources, firm economy and enormous manpower, US attacked Nazis with overwhelming force, who had occupied the whole of Europe except Great Britain and USSR. The US also provided Britain and USSR with extravagant supplies of food, trucks, weapons, boots and men. This considerably enhanced allies’ power and they finally succeeded in defeating the Nazis.
World War 2 ended with the defeat of Axis powers. This catastrophic war left more than seventy million people dead. This provided the people of the world a reason, horrifying enough to establish a world organization which will prevent such a catastrophe in the future. So the obsolete League of Nations was replaced by a more sophisticated United Nations (UN). But the end of Second World War also marked the rise of two powers, which were still energetic enough to claim the hegemony over the world. These were USA and USSR. The leader of USSR, Joseph Stalin was of the view that threat to communism could vanish only if more and more countries of the world adopt the communist ideology. But US would not let it happen. She was more interested in containing the communist USSR with hostile capitalist countries. This policy of US to contain USSR and eventually bring about its doom led the former to abandon its policy of isolationism and enter the world politics for better.
The rivalry between the US and USSR dragged on for about forty five years and this period of non-confrontation between them was termed as cold war. During this period they didn’t engage directly but there occurred some incidents which made the war between them imminent, like Korean crisis, U2 plane incident, Cuban Missile Crisis etc. Their mutual suspicion of each other and race to make more and more countries enter into their bloc, they spent extravagantly. The European recovery plan or Marshal plan of US and Molotov Plan of the USSR; the establishment of NATO by the US and establishment of Warsaw Pact in its response by the USSR; and finally the division of Germany into east and west are some of the proofs that how desperately they both wanted to oust the other one.
The reasons behind the US abandoning its policy of isolationism are multifarious.
They were to avenge the Pearle Harbor; to thwart Nazi idea to engulf the whole of Europe; to put a reign to imperialist Japan; to make the world safe for democracy and to establish a world organization which could replace the League of Nations. But these objectives were more or less temporary and after completing them US could have opted to retire back to the policy of isolationism, but the real factor which held her engaged in the politics of the world for so long was actually its rivalry with the USSR. If she had not contained the communist propaganda, the USSR would have no difficulty in propagating its policy of communism and majority of the world would have been in the grip of communism and USA would not have been in such a powerful position, which she is in,
today.

Time taken to complete the article: 1 hour 57 min.