During the last over 60 years there have been hundreds of research works published in Vietnam and abroad dealing with the history of Vietnam from 1939-45 and with the history of the Vietnamese August Revolution. However, there has still existed a very important problem unsolved: which power was in fact overthrown by the Vietnamese during the Vietnamese August Revolution of 1945? This studies is aimed to solve this problem. Based on newly collected documents and facts, the author pointed out clearly in this work that the power that was overthrown in August 1945 were the Tran Trong Kim’s Cabinet and the indigenous political system headed by it. Furthermore, the author tries to provide the readers with a detailed history of the Cabinet and then compares the existing interpretations concerning its nature, historic role and position. Finally, the author proposes a new balanced way to interpret the history of the Cabinet and the August Revolution in Vietnam. The study is really a new significant contribution to understanding of a very important period of Vietnamese modern history. It also provides an alternative way to interpret Vietnamese political history, particularly the issues concerning the political movements during the Japanese occupation and the birth of Vietnamese nation-state after the Second World War.