Many similarities exist between Vietnam and today’s war in Iraq. Even though every war is different in some major way(s), review of the United States withdrawal from Vietnam may provide some insight.
The treaty signed in January 1973 enabled the U.S. to fully withdraw its combat troops. By April 1973 the withdrawal was for the most part, completed. The war continued without the United States. In April 1975, the North Vietnamese Army attacked and took Saigon. We evacuated our embassy staff. Many people were imprisoned and/or killed during the months that followed. The point of view from the United States was, this is where it ended. The government of South Vietnam was gone. Once united, Vietnam left us alone.
A significant percentage of the population of the United States today is in favor of withdrawal from Iraq. Even an accelerated withdrawal would take at least a few months. How long do you believe the Iraqi government would last? If we use Vietnam as a guide (Possibly not an accurate indicator) Baghdad would last around two years. Once again, if we use Vietnam as a guide, many people would be killed over the next few months. After that, the new government of Iraq would leave the United States alone. If you believe this is likely, then it makes sense to agree with the idea that withdrawal from Iraq is a sound move.