Army Gen. David H. Petraeus assumed leadership of the U.S. military command charged with helping to build peace in a tough and war-torn part of the world Friday.

Petraeus took the reins of U.S. Central Command from acting commander Army Lt. Gen. Martin Dempsey in a ceremony at MacDill Air Force Base, Fla. Defense Secretary Robert M. Gates presided over the change of command held at the base’s Memorial Park.

“Gen. Petraeus, you are again taking responsibility for our precious sons and daughters,” Gates said. “I have no doubt they will continue to make you and me – indeed all Americans – very proud.”

Petraeus now has responsibility for the wars in Iraq and Afghanistan. He must deal with the threat that Iran’s pursuit of nuclear weapons poses to the region and world. He also must deal with an unstable government in Pakistan. U.S. Central Command reaches from Kazakhstan to Yemen and Egypt to Kyrgyzstan.

Petraeus commanded Multinational Force Iraq during the troop surge that turned the tide in Iraq’s security. Violence dropped in Iraq, and most of the country has returned to Iraqi control.

Before the change of command ceremony, Gates presented Dempsey with the Defense Distinguished Service Medal and Marine Sgt. Maj. Jeffrey Morin, U.S. Central Command’s senior enlisted leader, with the Defense Superior Service Medal.

The Senate has confirmed Dempsey for his fourth star and the post of commander U.S. Army Training and Doctrine Command at Fort Monroe. Dempsey – who was deputy commander of CentCom – took over as acting commander upon the retirement of Navy Adm. William J. Fallon in March. Marine Corps Lt. Gen. John R. Allen succeeded Dempsey today in CentCom’s No. 2 post.

“I recall my first meeting with Marty Dempsey after he took the reins of CentCom,” Gates said in his remarks. “He gave me a sheet of paper outlining the priorities for this command and asked for my guidance. After hearing what Marty had to say, I simply held up his own sheet of paper and said, ‘This is my guidance to you’ – a testament to his strategic vision and pragmatism, which he possesses in extra measure.”

Dempsey has been far more than a place-holder at U.S. Central Command, Gates said, and Navy Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, agreed.

“Here at CentCom, Marty truly made the words ‘acting commander’ a contradiction in terms,” Mullen said during the ceremony. “For there was nothing ‘acting’ about the way Marty has exercised the full spectrum of command throughout his entire area of responsibility. Nothing ‘acting’ about the way he orchestrated two wars at a critical time in our nation’s history.”

There also was nothing “acting” about his coordination with fellow combatant commanders and his management of the transition of Combined Joint Task Force Horn of Africa to U.S. Africa Command last month, Mullen said.

“Through it all, Marty has always placed the war-fighter at the forefront – a priority that he made clear on Day One – and he has responded at every turn with a quiet confidence that earned my admiration and that of countless others under his command and throughout the region,” the secretary said.

Gates next addressed the challenges awaiting Petraeus. “At the MNF-I change of command a few weeks ago, I said that history will regard him as one of our nation’s great battle captains,” Gates said. “He is the preeminent soldier-scholar-statesman of his generation, and precisely the man we need in this command at this time.”

The troops under his command, “dealt our enemies in Iraq a tremendous blow,” Gates said. “Now he will take aim at our adversaries in Afghanistan and lead security capacity efforts throughout the Middle East, the Gulf and Central Asia.”