Iraq committed multiple violations of the armistice treaty they signed (from a war they started)and did things like fire on America planes and try and assianiate our former presidents not to mention kicking out UN inspectors. After the fall of Iraq the people of Iraq decided to commit sustained war on each not to mention US troops and in the process drug extended the war years longer than the few months it should have lasted. What passed for a government in Afghanistan allowed their country to be used as a terrorist base to plan and train for attacks against the US.
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In both countries the war could have been short with a short occupation except for the fact that they choose to try and kill each other and drag it long after they had lost. If the Germans had behaved the way the Iraqis had behaved after loosing WWII it would have gone even worse for them because we are kindler and gentler nation now with a less friendly press corp.