Okay, so a long time ago in a country called Vietnam, there was a war happening where some people from one country called the United States went to fight against the people in Vietnam. During this war, some bad things happened where some people did things that were not okay and hurt other people.
After the war ended, some people wanted to look into what happened and figure out who did those bad things and make sure they were held responsible. So they created a group called the Vietnam War Crimes Working Group. This group was like a team of detectives who looked at evidence and tried to figure out what happened and who was responsible for those bad things.
They talked to a lot of people who were there during the war and looked at documents and pictures to try and piece together what happened. Sometimes it took a long time to figure it all out, but they kept working hard to find the truth.
Eventually, some people were held responsible for the bad things they did during the war, and this helped bring justice to the people who were hurt. The Vietnam War Crimes Working Group was an important part of making sure that people were held accountable for their actions and that justice was served.