The seventh death of a US soldier in Afghanistan so far in 2016, the Pentagon today announced an unidentified US service member was killed in an operation against the nation’s ISIS affiliate. The operation was in the Nangarhar Province, just a few miles from the Pakistan border.

Officials say an investigation is still ongoing to determine exactly what happened, but the soldier reportedly died during a foot patrol, as the result of an improvised explosive device (IED). It is unclear, according to those familiar with the situation, if the device was detonated remotely or not.

This incident is likely to add to questions about the nature of US operations in occupied Afghanistan, some 15 years after the initial invasion. While the US has repeatedly insisted the troops in Afghanistan are just advisers, they seem to be finding themselves out on patrol, and in harm’s way.

This was part of the third major anti-ISIS offensive in Nangarhar. In each of the previous offensives, US and Afghan officials declared quick victories, and claimed to have virtually totally expelled ISIS from the area, only to see them return almost immediately.