After more than 13 years in Afghanistan, U.S. commanders and their NATO allies lowered the organization’s flag in Kabul on Sunday, formally ending Operation Enduring Freedom and introducing a new mission — Resolute Support — in the country.

But there’s another related mission also now underway: Operation Freedom’s Sentinel. Defense Secretary Chuck Hagel said in a statement Sunday that will include two core components: working with allies and partners on Resolute Support, and continuing “counterterrorism operations against the remnants of Al-Qaeda to ensure that Afghanistan is never again used to stage attacks against our homeland.”

After 13 years, it’s a significant change for the military. “OEF,” as Operation Enduring Freedom is commonly known among rank-and-file troops, includes not only operations in Afghanistan, but efforts to target militants and train friendly militaries as part of OEF-Philippines and OEF-Trans Sahara. Like Operation Iraqi Freedom, the OEF acronym became a part of the troops’ lexicon and was incorporated in everything from awards to bumper stickers.

The Philippines mission has been slowly winding down. U.S. officials said in June that it was disbanding a Special Operations task force based there to train Philippine police and military forces as they face Abu Sayyaf extremists. Adm. Samuel Locklear, the outgoing chief of U.S. Pacific Command, said last April that the mission wouldn’t go away completely, but shift in part to focus on training a Philippine police force to protect its southern islands, where insurgents are active.

The Trans Sahara mission, meanwhile, ultimately took on the name Juniper Shield as it was broadened to include more countries across northern Africa, according to a 2012 report for the Congressional Research Service. The Web site noted that both OEF-TS and Juniper Shield were in use by the military earlier this year.

The Freedom’s Sentinel moniker was greeted with a mixed reaction Sunday. Some wondered whether it was “cool” enough, while others raised the question whether it sounded a little too much like something out of a comic book. It comes as the Afghan government struggles with a series of high-profile attacks and brutally high casualty numbers among its police and army units.

Hagel said that through “enduring security cooperation” the United States will continue to assist the Afghan government to build its capacity and self-sufficiency.

“We will continue to work with our Afghan partners to secure the great progress we have made since 2001 and to seize this defining moment of opportunity for Afghanistan’s future,” he added.