By Nancy A. Youssef | McClatchy Newspapers

WASHINGTON — Army Gen. David Petraeus, the commander who's been hailed for bringing stability to Iraq, became the 11th head of the U.S. Central Command on Friday, tasked with reshaping military efforts in America's other war, Afghanistan.

Petraeus took command from Lt. Gen. Martin Dempsey, who'd been the acting Centcom commander for seven months after Adm. William Fallon was forced to resign.

While violence in Iraq has dropped to some of the lowest levels since the war began, it's increasing in Afghanistan. U.S. troop deaths are at their lowest levels in Iraq but at their highest in Afghanistan, where the Taliban continues to operate from its refuge in neighboring Pakistan. Some believe that the Taliban is trying to encircle the Afghan capital of Kabul.

Petraeus has called the war in Afghanistan, now in its seventh year, America's "longest campaign."

He's leading an assessment of the U.S. strategy in Afghanistan, Pakistan and beyond, to define the U.S. objectives and determine if the U.S. military and civilian leadership can achieve them. That the U.S. is asking such questions seven years into the war in Afghanistan speaks to the dire state of U.S. strategy. The assessment is also examining to what extent a troop "surge" like the one that Petraeus engineered in Iraq could be effective in Afghanistan.

During Friday's ceremony, Petraeus referred to the "innumerable challenges" in his new command area.

So far, Petraeus has suggested that Afghanistan not only needs more troops, but also a reconciliation plan with some Taliban members. In addition, U.S. officials have suggested that the military must link its Afghanistan and Pakistan strategies.

Both presidential candidates also have called for sending more troops to Afghanistan. But to send more troops, military officials have said they must withdraw troops from Iraq. There are 152,000 American troops in Iraq and 32,000 in Afghanistan.

Petraeus is expected to travel to Afghanistan soon.

Centcom, which is headquartered at MacDill Air Force base in Tampa, Fla., is responsible for U.S. operations in 20 nations that stretch from Egypt to Kyrgyzstan. There are roughly 250,000 U.S. forces deployed in that region.

Petraeus left his post as the Iraq commander in September after leading the U.S. effort there for 18 months. Dempsey will earn his fourth star and command the U.S. Army Training and Doctrine Command.

MORE FROM MCCLATCHY

Another success? Iraqi mayor Bush once hailed flees to U.S.

Top U.S. commander warns that Afghan war could get worse

Odierno: Former door-kicker now reflects Iraq progress

Petraeus, credited with Iraq progress, recalls agonizing day in '07