Confidential documents are confidential because the information recorded in them has a great dynamic effect on the then Political and Economic Bureau. In layman's terms, his exposure can change the world, such as the stepping down of the president and the exposure of military actions, which were presented to people at that time in a vague way. The public wanted to get in touch with the truth, so the things recorded in these secret documents would not have that great effect after they became "history". For example, many secret moments during World War II, the Normandy landing, the planning of the Battle of El Alamein and so on. These events were announced after the war, which filled the gap in history and became an inseparable part of history.