The end of the Second World War brought many photo opportunities for the victors. The Soviets and the Western Allies had promoted the concept of an antifascist brotherhood during the war, and photos were taken all over the world of the Allies embracing and celebrating their victory.
Before the war ended, the three major Allied nations began to discuss the postwar world in a series of conferences with the three leaders. Roosevelt, Churchill, and Stalin met at Yalta in March 1945 and Truman, Atlee and Stalin met in Potsdam in July 1945. Roosevelt had first used the term "United Nations" when 26 Nations signed the Declaration of the United Nations on January 1, 1942. From April to October 1945, 51 nations met in San Francisco and created the United Nations. The Headquarters were set up in New York after the Charter was ratified by a majority of the member nations. The major Allies (China, Soviet Union, France, Great Britain, and the United States) held seats on the Security Council, each country held veto power over any decision the United Nations made.
The reality was that huge cracks were appearing in the Allied unity. With no more enemies to fight, the suspicions held at bay until victory was obvious became public and bitter. Churchill later wrote that he already suspected the Soviets were replacing the Axis as the aggressors before the European war ended.
America, enjoying a brief monopoly on the atom bomb, conducted tests in the Bikini Atoll on July 25, 1946. The world was impressed by the casual destruction of so many warships as much as it was by the bomb itself. The Berlin Airlift heightened the Cold War tension in 1948. In 1949 the Western Powers came together to form the North Atlantic Treaty Organization (NATO). When the Soviets and soon the French, British, and Chinese acquired the bomb, huge arsenals were quickly built. The ability to annihilate the planet many times over evolved into the concept of Mutual Assured Destruction (MAD) which meant that neither side would start a war if they were guaranteed to be destroyed.