Not Daesh. Not ISIL. Not IS.

The Pentagon has officially declared the name of the terror group the United States and its allies have been fighting for years is, in fact, ISIS.

“We have officially switched to ISIS,” Capt. Jeff Davis, a Pentagon spokesman, said in a briefing with reporters Friday. “They all mean the same thing.” Davis said ISIS already had been used unofficially in the past inside the Pentagon because it was the “easiest to understand.”

While “ISIS” has been widely accepted for years as the common acronym for the Islamic State, then-Secretary of State John Kerry and others in the Obama administration insisted for years on using “ISIL” or “Daesh,” the acronym formed using Arabic letters to spell Islamic State in Iraq and Syria.

The Pentagon released a memorandum Friday afternoon dated Feb. 13 outlining the official change.

“We view ISIS, ISIL and Da'esh as interchangeable terms for the same thing. ISIS is the term most known and understood by the American public, and it is what our leadership uses. This memo simply aligns our terminology,” Davis said in a statement attached to the memo.

In the months leading up to the election, then-candidate Donald Trump blasted then-President Barack Obama for not using the phrase “radical Islamic terrorism.”

He didn't use the phrase because he insisted, “loose language that appears to pose a civilizational conflict between the West and Islam, or the modern world and Islam, then we make it harder, not easier, for our friends and allies and ordinary people to resist and push back against the worst impulses inside the Muslim world,” Obama told The Atlantic’s Jeffrey Goldberg.

Obama also didn’t want the fight against ISIS, Al Qaeda or the Taliban to appear to be a “clash of civilizations” a phrase made famous by the late academic Samuel Huntington in an article by the same name. Instead, Obama and his administration used the phrase “violent extremism” to describe the terror threat.

Trump and his top advisers on the campaign trail insisted the threat facing the United States was much greater than Obama presented to the American people.

On Thursday at a Washington think tank, Chairman of the Joint Chiefs of Staff Gen. Joe Dunford, who served under Obama and now Trump, was asked why he continues to use the phrase “violent extremism” to describe terrorist groups.

“If you talked about a specific group, I'd give you a more accurate descriptor,” said Dunford. “I was using the term violent extremism to refer to all of those groups … individuals who take up arms to advance political and/or religious objectives.”