Unfortunately, history does suggest that the War in Afghanistan cannot be won. The War in Afghanistan has been underway for more than a decade. The United States is fighting against an enemy that is easily hidden, much like the VietCong during the Vietnam War. If we look at the patterns of history, especially of conflicts during the Cold War, it is easy to see how the conflict will never be resolved, no matter how many troops are sent.
Today's war in Afghanistan has nothing to do with previous military campaigns there. Alexander the Great was defeated, and so were the British and the Soviets. Yet today's military has far more advanced technology, and their goals are totally different. The Americans are trying to fight terrorists, not colonize or conquer the land, like most historical examples.