What are two military factors that led the u. s. to end its involvement in vietnam? if you can have evidence?

America wanted to stamp out Communism in South East Asia. They also looked at this an an opportunity to fight the soviets but not directly , this is called a proxy war. Such proxy wars happened in Afghanistan and Korea and now in Syria. For evidence , the United states president at the time lyndon b Johnson said " the Soviet threat is only going to get bigger and we have to take âction now"