Afghanistan is a country that has proved to be extremely difficult to invade, and that has been the case for thousands of years. There is one major reason for this, the geography of the country. The country is dominated by very high mountains that create rain shadow and and deserts. The mountains themselves are extremely difficult for passing through, and even if they are passed by an invading army, they will take their toll. Once the mountains are passed, an invading army would face desert, very dry climate, very few food sources and very little water, with temperatures varying from scorching hot in the summer, to freezing cold in the winter. So even if an army passes through both of these natural obstacles, when it comes to face the natives it will be too weak to invade.
