Updated

Gen. Stanley McChrystal, a former top special operations commander, took charge of nearly 90,000 U.S. and NATO troops in Afghanistan on Monday, telling them they must protect Afghan civilians from all kinds of violence.

McChrystal takes over the Afghan campaign at a critical moment: violence, troop levels and U.S. military deaths have all hit record highs, and President Hamid Karzai has increased pressure on U.S. forces to prevent civilian deaths.

Seeking to shake up the direction of the war, Defense Secretary Robert Gates sent McChrystal to lead the 42-nation effort in Kabul in the middle of U.S. Gen. David McKiernan's two-year assignment, effectively ending the career of a four-star general whom McChrystal called a "fellow soldier and friend."

McChrystal is expected to take a more unconventional approach to the increasingly violent campaign in Afghanistan, relying on decades of experience with special operators — elite military units like Navy SEALs and Army's Delta Force that carry out dangerous and secretive missions.

Speaking before several hundred troops at a ceremony filled with colorful flags and a military band at a heavily fortified base in central Kabul, McChrystal said the international mission "must recapture the excitement and inspiration that ignited this country" after the 2001 fall of the Taliban regime.

He immediately addressed civilian casualties, an issue Karzai warned the general about when the two met Sunday.

"The Afghan people are at the center of our mission. In reality, they are the mission. We must protect them from violence, whatever its nature," McChrystal said. "But while operating with care, we will not be timid."

As he spoke, a U.S. flag fluttered softly at half staff over his right soldier in a silent reminder that the war is on a pace to claim a record number of American lives. Seventy-four U.S. troops have died in Afghanistan this year, a rate that will likely surpass the record 151 killed last year.

The relationship McChrystal has among the military's special operators — forces that have been involved in some of the deadliest civilian casualty cases in Afghanistan — is seen as one of his key assets.

Navy Rear Adm. Greg Smith, a new one-star commander sent to Kabul to help shape the military's public relations efforts, said McChrystal can tell those forces that "every single decision has to be considered in the strategic context" — including a firefight leading to a dropping of bombs that might kill civilians.

McChrystal will visit commanders around Afghanistan this week and communicate that message "in a real clear tone," Smith said. The commanders will likely discuss civilian casualties during the McChrystal's "listening tour," and he may issue updated guidance to troops afterward, Smith said.

In new guidelines issued today, McChrystal told troops they must know "precisely what effects will be caused by our actions," Smith said.

The top U.N. representative in Afghanistan, Kai Eide, told NATO defense ministers in Brussels on Friday that there is "an urgent need to review the operations of special forces." Civilian casualties overshadow the positive trends in Afghanistan, he said.

"The political costs are simply disproportionate to the military gains," Eide said.

McChrystal will command the largest international force ever in Afghanistan. A record 56,000 U.S. troops are in the country, alongside 32,000 troops from 41 other countries.

President Barack Obama has increased the U.S. focus on Afghanistan this year, ordering 21,000 new troops to the country even as the U.S. begins to pull troops out of Iraq. There is expected to be about 68,000 U.S. troops in Afghanistan by the end of the year.

American Marines have poured into Helmand province over last several weeks in an effort to stamp out an insurgency that has a strong hold in the world's largest opium poppy-growing region.

Militant attacks have risen steadily in the last three years and have reached a new high. Afghanistan saw 400 insurgent attacks during the first week of June, an eight-fold increase over January 2004, according to U.S. Gen. David Petraeus.

On Sunday, Karzai warned McChrystal that the "most important element of the mission" is to protect Afghan civilians.

Civilian casualties during military operations have long been a point of friction between Karzai and the U.S. The most contentious civilian deaths in U.S. military operations in recent years have involved U.S. Special Operations Forces, which McChrystal commanded from 2006 to mid-2008.

In early May, dozens of civilians were killed when U.S. and Afghan troops backed by U.S. fighter aircraft battled militants in southwestern Farah province. The Afghan government says 140 civilians died, while an Afghan human rights group says about 100 died. The U.S. says no more than 30 civilians were killed in addition to 60 to 65 militants.

McChrystal has already pledged to review operating procedures with an eye to minimizing civilian deaths.

"Although I expect stiff fighting ahead, the measure of effectiveness will not be enemy killed," he told Congress this month. "It will be the number of Afghans shielded from violence."