The history of this country extends back to the days of Alexander the Great. After falling to the Parthians and thriving as a Buddhist entity, the country was conquered by Islam, only to fall to the forces of Genghis Khan in the early 13th century. After a period as the center of Tamerlane's empire a century-and-a-half later, the country was broken up and controlled by a number of small kingdoms and tribes. In the mid-eighteenth century, a unified emirate was established by Ahmed Shah Durani. Eventually, the country was controlled by Britain, and it was not until 1919 that Afghanistan achieved full independence under Amanullah Khan, who was proclaimed king. The monarchy was overthrown in a military-led coup in 1973 and the country descended into a civil war, following the 1979 Soviet invasion. (A pro-Soviet coup had taken place in 1978). A decade later the USSR withdrew. Turmoil has continued to dog the country with the rise of the extreme fundamentalist Taliban, which since 1995, have overrun the country and instituted a strict Islamic-based regime. In late 2001 in wake of the terrorist attacks on the World Trade Center and the Pentagon, the United States began providing air and ground support to the forces fighting the Taliban. The Taliban regime was defeated and an interim government led by Hamid Karzai.