One of President Barack Obama's first moves as president was to order a troop surge of about 33,000 soldiers to Afghanistan to clamp down on Taliban attacks. Now, more than two years after they arrived, the last of the surge troops is heading home, according to The Associated Press.

Defense Secretary Leon Panetta marked the occasion on Friday and said the surge served its purpose. However, while the 33,000 soldiers have left, there are still about 60,000 American troops on the ground in Afghanistan, all of whom are slated to leave by the end of 2014.

"The surge did accomplish its objectives of reversing the Taliban momentum on the battlefield and dramatically increasing the size and capability of the Afghan national security forces," Panetta told the AP.

There are still considerable challenges facing American forces still in Afghanistan. Among the most serious obstacles are the rise of insider attacks, where Afghan troops kill American soldiers. So far this year, 51 servicemembers have been killed in such attacks.

With the withdrawal of its surge troops, the United States remains on pace to fully leave the country by 2014. Despite the insider attacks, White House officials tout the fact that 330,000 Afghans have joined the national forces.