For over 2,500 years, the forbidding territory of Afghanistan has served as a vital crossroadsnot only for armies but also for clashes between civilizations. As the United States engages in armed conflict with the current Afghan regime, an understanding of the military history of that blood-soaked land has become essential to every American.Afghanistan's military history provides lessons for us today. The earliest written records inform us of fierce mountain tribes on the "eastern" edge of the cradle of civilization. Alexander the Great conquered Afghanistan on his way from Persia to India. Later, because of its strategic locationthe Silk Road passed through its mountainous northern regionAfghanistan was invaded in succession by Arabs, Mongols, and Tartars. In the nineteenth century, Great Britain triedand failedto add Afghanistan to its Indian empire, while Russia tried to expand into the same embattled land. Afghanistan once again foughtand defeated Russia in the 1980's when it tried to prop up a secular government in the face of rising Islamic resistance.Now America must face a new enemy on this landa land that for centuries has become a graveyard of empires past.