The killing of a Navy SEAL by Islamic State fighters highlights the increasing risks US troops face in Iraq and Syria as they inch ever closer toward the jihadists' frontlines.
IS fighters on Tuesday used suicide bombers and firepower to blast their way past Kurdish peshmerga forces that US troops were supporting north of Mosul in northern Iraq.
The fallen SEAL had been visiting a peshmerga encampment near Tal Asquf about three miles (five kilometers) from the front. Officials simply said he was killed by "direct fire."
Arizona Governor Doug Ducey identified the SEAL as Charlie Keating IV, who attended high school in Phoenix.
It is only the third time a US serviceman has been killed in combat since the United States launched an international coalition to fight the IS group in August 2014. Another 14 have been wounded.
Since the start of the campaign, the US military and its coalition partners have launched more than 12,000 air strikes against the self-proclaimed Islamic State group, and the Pentagon has deployed around 5,000 troops in Iraq.
The effort is primarily being conducted by plane and drone strikes, but America's intensifying role for troops on the ground means additional US casualties are likely.
"Although the US has pursued a light-footprint policy to try to minimize the number of combat troops it has on the ground, at the end of the day these soldiers are serving in a conflict zone and there will be casualties," Nick Heras of the Center for a New American Security told AFP.
Last month, the Pentagon said US military advisors will start working with Iraqi forces at the battalion level, meaning greater numbers will be physically closer to the fight in Iraq than before.
And the United States has increased sixfold -- from 50 to 300 -- the number of special operations forces and support personnel working in northern Syria, where they are training Kurdish and Syrian Arab fighters to tackle the IS group and call in air strikes.
"It's certainly inevitable that the more US forces become involved in supporting ground operations, the more risk they are going to have to take," said Jacob Shapiro, an associate professor at Princeton University.
Officially, more than 4,000 US forces are in Iraq, but when temporary assignments are factored in, the number stretches beyond 5,500.
Rocket fire killed a US Marine in northern Iraq in March, while a special forces soldier died of wounds received during a raid in October.
The casualty numbers are tiny compared to the US-led wars in Iraq and Afghanistan, where more than 5,300 US troops were killed in combat.
President Barack Obama, elected partly on a promise of getting America out of Iraq, has faced a backlash at home for saying there will be no US combat "boots on the ground" in the Middle East -- even as US troops die in combat.
"Our men and women on the ground in Iraq do not have a combat mission, but they do have a dangerous mission to operate in a dangerous country," White House spokesman Josh Earnest said.
Obama's policy is to use US troops to train, advise and equip Iraqi and Syrian forces to fight the IS group.
The immediate goal is for them to retake the key IS cities of Mosul in Iraq and Raqa in Syria, but it is unclear if local forces have the capabilities to hold the towns.
"We have learned important lessons in the last decade. We know that the United States will not be successful if it is US troops acting, essentially, as a substitute for local forces fighting for the security situation in Iraq," Earnest added.
Critics have called Obama disingenuous for deploying US troops without describing their role as a combat mission.
"Why does the administration go through these crazy somersaults, that the entire country knows is not correct, to say our troops are not in combat when they're in combat?" Senator Dan Sullivan asked Defense Secretary Ashton Carter at a hearing last week.
"These people are in combat, senator, and I think that we need to say that clearly," Carter responded.
Obama's term finishes at the end of the year. His potential successors have indicated a willingness to deploy more US forces to the region, but the US public has little appetite for such an engagement.
"There is no chance of large-scale combat," said Michael O'Hanlon, a senior fellow in foreign policy at The Brookings Institution.
"I could imagine American troops in the thousands or, in an extreme case, the very low tens of thousands but not main combat operations, even under a new president. We already tried that."