The designated U.S. ambassador to Afghanistan, Lt. Gen. Karl Eikenberry, retired from the Army on Tuesday to become one of the few generals in American history to switch directly from soldier to diplomat.

After being sworn in at the State Department on Wednesday as the top U.S. envoy to Kabul, Eikenberry will return to the war-torn country where he served as the senior U.S. commander just over two years ago.

Eikenberry takes the diplomatic stage at a perilous time in the nearly eight-year conflict. Insurgent violence is rising as the Obama administration seeks to implement a new strategy that puts added emphasis on nonmilitary means of stabilizing the country and preventing it from becoming a terrorist haven.

At a retirement ceremony in the Pentagon's Hall of Heroes, Eikenberry said he will begin his tenure in Kabul under "extraordinarily difficult conditions" but expressed confidence that the new strategy would succeed.

One of the people he will work with most closely is Gen. David Petraeus, the Central Command chief responsible for U.S. military operations in Afghanistan and Pakistan. Petraeus attended the ceremony, which was hosted by another key figure in the war effort, Adm. Mike Mullen, chairman of the Joint Chiefs of Staff.

The son of a World War II veteran and a native of Goldsboro, N.C., Eikenberry has previous experience in the political-military arena, including a stint as the U.S. defense attache in Beijing and as a senior officer at NATO headquarters. He is fluent in Chinese and a scholar of Chinese history. He has two master's degrees -- one in East Asian studies from Harvard and another in political science from Stanford.

"Karl Eikenberry's talents are ideally suited to the president's new, comprehensive strategy in which he must get the civilian parts of our effort right," Mullen said. "Karl's experience as a soldier and scholar will be crucial to fostering the strong civil-military relationship required to tip the balance."

Eikenberry joked that he and his wife, Ching, will enjoy a "24-hour vacation" before Wednesday's swearing-in ceremony to be hosted by his new boss, Secretary of State Hillary Rodham Clinton.

Eikenberry's retirement from active Army duty is effective Friday. He is due to start in Kabul on May 8.