U.S. forces have left one of the largest military bases in Afghanistan, according to three defense officials, writes NBC news.

The Kandahar Airfield was turned over to the Afghan National Defense Security Forces earlier this week, the officials said, in a move that signals the urgency of the U.S. effort to fully withdraw from the country by Sept. 11.

Located in southern Afghanistan, Kandahar has been one of the main bases housing U.S. and international troops. At its height, the sprawling military base and airfield were home to more than 26,000 U.S. and international troops.

When coalition combat operations officially transitioned to a training mission in late 2014, Kandahar became the training hub for the southern region of Afghanistan.

Kandahar is historically significant as the birthplace of the Taliban and the last major city where the United States drove the extremist Islamic movement from power in 2001. Since then, Taliban fighters have continued to try to regain control of the city, often taking over towns and areas in Kandahar province for short periods of time until being driven out again.

Last month, the Taliban targeted the Kandahar Airfield with a rocket attack that did not cause any casualties or damage.

The U.S. military is in the midst of withdrawing all of its roughly 2,500 troops from Afghanistan.