This is a very broad question, so I'll give a very broad answer; if you have specific questions about a place or an aspect of any of this, please follow up.

The end of the fighting did not restore trade or infrastructure; in much of Europe and Asia, it would take time to grow harvests and re-establish supply routes disrupted by war. Many people were weakened during the war, by wounds or starvation or illness, and succumbed to these wartime injuries or traumas. The most obvious groups here would be concentration camp prisoners in Europe and victims of atomic bombing in Japan.

Vast numbers of refugees moved around the former war zones; millions of forced laborers left Germany for their homelands. Millions more ethnic Germans were expelled from countries across Europe. As the Soviets consolidated control in Eastern Europe, they launched bloody purges of Nazi collaborators and especially of former Soviets who had fought for Germany, or were suspected of insufficient resistance.

In Asia, millions of Chinese migrated back into Japanese-held areas, but China remained at war for another four years; Chiang's Nationalists fought Mao's Communists viciously, pushing them back into Manchuria before overextending themselves and collapsing. A flood of U.S. equipment was vital to this effort, and it was backed by thousands of U.S. Marines who guarded ports and railroads, freeing up the Nationalists to fight.

70,000 U.S. Marines were stationed in China over the next four years, occasionally skirmishing with Mao's Communists throughout the Chinese Civil War. Chiang had ordered many Japanese units to maintain order until their surrender was formally accepted, and so in large parts of China Japanese military units continued to fight the Communists for months or even years before being relieved and sent back to Japan; in December 1945, there were still about 400,000 Japanese soldiers who remained at their posts. In one memorable October 1945 incident, U.S. Marines were taking a train with several hundred Japanese soldiers to the coast when they were stopped by Communist soldiers; the Marines responded by arming the Japanese soldiers. This could have been the only instance of Imperial Japanese forces and U.S. Marines fighting side by side in combat, but the Communists withdrew and the Japanese commander formally returned his unit's arms.

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