Answer:
Main points are: In the early 1970s, the U.S. began to retreat troops from Vietnam, "lessened" their direct involvement, simultaneously negotiating a "peace deal" that the U.S. proceeded to violate heavily as a last attempt to win the war before giving in and officially signing it in 1973, finally ending the unwinnable war.
Step-by-step explanation:
I somehow cannot post the whole explanation + brief timeline part here, so DM me if you'd want that part.