"Home By Christmas"

It seems that all empires have some sort of diluted idea as to what the cost of war is and how difficult foreign occupation is. In talking about the American invasion of Iraq, and wether or not America should be considered an empire, Parsons mentions "As a result, the price of operation Iraqi Freedom, which Rumsfeld and his planners assumed would last only a few months and cost forty to fifty billion dollars, reached approximately 3 trillion dollars by 2008." (P. 445) Now this is not the first time that we have seem military planners severely underestimate the length that war would last. The most famous of which would be from World War One, in which the slogan "home by Christmas" was the belief of the day. There are other instances as well, both Hitler and Napoleon believed that they could nock out Russia before winter set in. Why is it that empires always seem to grossly underestimate how long a campaign is going to take? Is it underestimating the strength of their enemy? This would make sense, but it seems to be something else. It seems to be that empires do not realize how costly an occupation is until they are actually in the act of doing. Occupation is something that happens on such a large scale and requires hundreds of thousands of men. It seems that most Empires forget about this, and they forget about the resistance that they will receive once the country appears to be "occupied". All of this then runs up the price tag that the invading army will then have to pay to such obscene numbers and causes the way to drag on and on that it will be nowhere near the original time plan that they had set in place for themselves. Empires when occupying need to remember that once that battle is over, if they plan to occupy it will not be a few month process, this is a much longer process that is extremely expensive. Yet, history has shown us that empires have and will continue to invade on a premise that they will be "home by Christmas" or some other slogan that they can develop to convince both their soldiers and civilians that the war will only last a few months.