WASHINGTON — Among the troops Defense Secretary Leon Panetta will see Friday when visits Fort Campbell, Ky., are several hundred soldiers preparing to begin ground-level implementation of the American endgame in Afghanistan.

Starting in April, the Army will send scores of 18-soldier teams throughout Afghanistan to train and advise Afghan soldiers and police, groups that have increasingly turned their guns on the international troops working with them. The latest incident came Thursday when a man in an Afghan army uniform and another in civilian clothes shot and killed two NATO troops, bringing to six the number of coalition forces killed in such attacks within the last two weeks.

Despite the violence, a range of military leaders and analysts have called the Security Force Assistance Teams, or SFATs, the key to the NATO coalition strategy of progressively turning over the lead in the fight against the Taliban.

“What’s particularly troubling is you have the spike of these incidents at a time when we’re shifting our strategy to the advisory paradigm,” said Juan Zarate, former deputy national security advisor for combating terrorism and current senior advisor at the Center for Strategic and International Studies.

Nearly 1,500 soldiers are scheduled to deploy by the end of August, enough for about 80 such teams. They will be comprised of officers and experienced NCOs plucked from six units nationwide, including the 2nd Brigade Combat Team of the 101st Airborne Division at Fort Campbell.

According to Army Chief of Staff Gen. Ray Odierno, speaking last week to reporters, a growing number of SFATs will progressively replace all combat units as the U.S. combat role nears its scheduled end in December 2014.

Many thousands of U.S. troops have already trained Afghan security forces. But the SFATs — small groups embedded with far larger units of Aghan soldiers and police in cities and villages nationwide — represent the model on which the Defense Department plans to base the Afghan transition.

“We’re the gateway on pulling out of Afghanistan,” Staff Sgt. Jacob Fizer, a Fort Polk, La., machine gunner and SFAT member from the 191st Infantry Brigade, said in an Army news release last week.

But the possibility that groups may also become targets of disgruntled Afghan forces has raised doubts about the overall U.S. strategy. How resilient will the U.S. be if its embedded troops continue to be killed by those the aim to help?

Already there are indications that killings of troops can tie the advisory strategy in knots, at least temporarily. In the aftermath of outrage over the inadvertent burning of Qurans on a U.S. base, the murders of two American troops working in the Afghan Interior Ministry in Kabul last Saturday prompted the top U.S. commander in the country, Gen. John Allen, to pull U.S. advisers from government ministries. Only on Thursday did some begin to return.

With the Taliban working to drive wedges between Afghans and foreigners in the country, particularly those who work together in uniform, the United States and its military have to accept some risk to bring an orderly end the war and give the Afghan government the ability to defend itself from insurgent attack. Controlling the risk is the key, Zarate said.

“I don’ t think you jettison the strategy,” he said. “Instead, you do everything you can to ensure the safety of the advisors.”

The Army on Wednesday declined to provide information on how the SFAT units would handle security.

But Army spokeswoman Lt. Col. Margaret Kageleiry said force protection while embedded would be a priority.

“Soldiers routinely work to maintain situational awareness and personal security as part of their missions,” she wrote in an email.

Retired three-star Gen. David Barno, a senior advisor at the Center for New American Security, a Washington think tank with close ties to the Obama administration, said the violence of recent days is likely prompting the deploying SFATs and their commanders to take another look at security.

Barno, commander of Combined Forces Command-Afghanistan from 2003 to 2005, said the key will be for SFAT soldiers to quickly build personal relationships with members of Afghan units they’re operating within – and then keep an eye on them.

“I think there’s going to be a lot of focus the next few weeks ... on counter-intel and perceiving threats in the force they’re working with,” he said.

Another likely measure, he said, is “a member of each team responsible 24/7 for security.”

The United States must do what it takes to make the SFAT mission work, said Barno, who authored a CNAS paper recommending the advisory strategy in the weeks before Army and Defense Department leaders began to embrace it.

“That’s the only coherent strategy we have in terms of preserving our vital national interests in that part of the world,” he said.

carrollc@stripes.osd.milTwitter: @ChrisCarroll_

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