The American general who led the ground invasion of Iraq took command of the 40-nation NATO-led campaign in Afghanistan on Tuesday.

Army Gen. David D. McKiernan took charge of the 51,000-member International Security Assistance Force from Gen. Dan McNeill, who will retire from the U.S. Army after 40 years.

Addressing a change of command ceremony Tuesday, McKiernan said he was "honored to walk alongside our Afghan brothers."

"While today marks a transition in commanders, the mission must continue without missing a beat," he said, listing security, reconstruction and development as the types of support that Afghanistan deserves. "Insurgents, foreign fighters, criminals and others who stand in the way of that mission will be dealt with."

Afghan President Hamid Karzai welcomed McKiernan to the country.

"Your task will not be easy," Karzai warned. "But I'm sure as good a soldier as you are, you will serve it well, together with Afghan officers and the Ministry of Defense."

He asked McKiernan and other military commanders to continue to equip and train Afghan security forces so the country can eventually stand on its own.

McKiernan, whose previous assignment was as commander of the U.S. Army in Europe, inherits the largest ISAF force since the international military partnership was created in 2001, shortly after the U.S.-led invasion of Afghanistan to oust the Taliban for hosting al-Qaida chief Osama bin Laden.

He takes command during a period of heightened violence and a spiraling opium poppy heroin trade in Afghanistan. More than 8,000 people were killed in insurgency-related attacks in the country last year, the most since the 2001 invasion.

But McKiernan will also have more Afghan army troops and police — about 130,000 — working alongside ISAF forces than any previous commander.

As a three-star general in 2003, McKiernan commanded the U.S. land forces during the invasion of Iraq.

Around the country, three policemen, a private security guard and at least 10 Taliban were killed in Afghanistan's latest violence.

— In the Murja district of Helmand province, Taliban fighters attacked a police patrol Monday and killed one policeman, said provincial police chief Mohammad Hussein Andiwal. Police counterattacked, killing eight Taliban.

— In the eastern province of Khost, gunmen assassinated a district intelligence Tuesday, said Mujib Rahman, the district chief of Alishar.

— In the southern Zabul province, Taliban fighters ambushed a NATO logistics convoy and killed one private security guard, said provincial police chief Saridullah Khan.

— U.S.-led coalition forces killed "several" militants during an operation in the Garmser district of Helmand province Monday, the coalition said. Militants attacked the coalition troops while they were searching a compound, and the troops responded with gunfire, mortars and air strikes, killing the militants, the coalition statement said.

U.S. Marines moved into Garmser in early May, and NATO officials say that militants who used to operate there are starting to flee the region.

— In Herat province's Ghoryan district, Taliban attacked a police checkpoint, killing one officer and kidnapping six, said Haji Raouf Ahmadi, police spokesman for western Afghanistan.