Peshmerga in a defensive position, preparing for an incoming ISIS assault. Courtesy of Peshmerganor It had been relatively quiet for a month when in the morning of May 3 one of the largest assaults from Islamic State militants began.

More than 120 ISIS fighters, 20 armored vehicles equipped with crew-served weapons, and at least one bulldozer attempted to push into Tel Askuf, a once predominately Christian city, about 20 miles north of the ISIS-held Mosul.

In their minds, the jihadists had good reason for their surprise attack: According to Kurdish sources, within the town's walls were a handful of US advisers who had been assisting the local Kurdish peshmerga forces along with the Asayish, a Kurdish security and intelligence agency, and several Christian militiamen.

After about 20 minutes, ISIS fighters managed to punch through the peshmerga frontlines and advance toward Tel Askuf. When the US advisers in the town finally made contact with ISIS forces, the area's Quick Reaction Force was called, and about 20 Navy SEALs arrived with weapons at the ready.

About two hours in, however, one of the QRF members, Naval Special Warfare Operator 1st Class Charles Keating IV, was hit by small-arms fire after climbing to a roof to pick off ISIS militants. A Black Hawk medevac was called in to evacuate the wounded, but Keating's injuries proved to be fatal.

The ensuing battle was so fierce that additional aerial support was required — A-10s, F-15s, F-16s, B-52s, and drones were all scrambled to assist the ground forces. Ultimately, ISIS was forced back from Tel Askuf.

Keating, 31, an Arizona native, was posthumously promoted to chief petty officer.

"This was a large fight, there's [no] question about it," Col. Steve Warren, a spokesman for the US Department of Defense, said.

Though media coverage has centered on the scenes in Tel Askuf, Business Insider obtained new footage from a peshmerga soldier who claimed to be on the frontlines against the initial ISIS assault. If the following images and associated reports are valid, they would depict not only the chaos and fear from ISIS' attack on the frontlines, but also the dangers that US medevac helicopters face to ensure a servicemember receives medical care.

We have turned the footage into a series of stills below.

Warning: The following images may be too graphic for some.