The years 1962 - 1963 roughly correspond to the visible ramping up of regular U.S. infantry ground forces in Southeast Asia.  While sure, a lot of American activity had been going on previously involving MAAG, Special Forces, Air America and other CIA types, the emotional "beginning" of the Vietnam War for many if not most Americans can be bookmarked at the point the "Boy Next Door" fatalities began to be reported in numbers too big and too often to ignore, especially after at least one notable general predicted American victory by the end of 1963.

But the idea the boys would all come home by Christmas is an old one, and probably had its beginnings well before World War I or the American Civil War.