By 1965 there were over 80,000 troops stationed in Vietnam. There were almost 200,000 troops that were being ordered to come fight alongside them. As fighting continued more and more troops were being called in. By 1967 500,000 US troops were overseas fighting the Viet Cong. The Viet Cong responded to this by coordinating a series of surprise attacks on Southern Vietnamese cities. This assault became known as the Tet Offensive and caught the US and Southern troops completely off guard. The US quickly retaliated recapturing the cities and calling 200,000 troops in to fight.