World War I...four years (American involvement - 19 months).
World War II...six years (American involvement - four years).
Korean War...three years.
President Eisenhower delivers farewell address warning against the military industrial complex 1961:
Vietnam War...sixteen years (full-scale engagement - twelve years)
Now the White House says America will be out of Afghanistan in 2017 - that's sixteen years for the greatest military in the history of mankind to defeat a bunch of cavemen, bedouins and goat herders. When do the American people finally figure out that war is a racket?