Occupying a nation that has faced an overwhelming military defeat is a lot different than sending a glorified version of the Peace Corps to maintain law and order in a Third World sh!t-hole.
150,000 men is hardly a peace corps contingent. The Russians, of course, had a much larger force in Afghanistan with less result that we have in that country, and still have not pacified Czechen despite a much higher butcher's bill than we have paid.