Following the defeat of Nazi Germany, World War II Allies including the U.S., Britain, and Soviet Union, hold the Potsdam Conference in Germany to plan the post-war world. Vietnam is considered a minor item on the agenda.
In order to disarm the Japanese in Vietnam, the Allies divide the country in half at the 16th parallel. Chinese Nationalists will move in and disarm the Japanese north of the parallel while the British will move in and do the same in the south.
During the conference, representatives from France request the return of all French pre-war colonies in Southeast Asia (Indochina). Their request is granted. Vietnam, Laos and Cambodia will once again become French colonies following the removal of the Japanese.