ISIS has lost 98 percent of the territory it once held -- with half of that terror group's so-called "caliphate" having been recaptured since President Trump took office less than a year ago, U.S. military officials said Tuesday.

The massive gains come after years of "onerous" rules, when critics say the Obama administration “micromanaged” the war and shunned a more intensive air strategy that could have ended the conflict much sooner.

“The rules of engagement under the Obama administration were onerous. I mean what are we doing having individual target determination being conducted in the White House, which in some cases adds weeks and weeks,” said retired Air Force Lt. Gen. David Deptula, the former head of U.S. Air Force intelligence. “The limitations that were put on actually resulted in greater civilian casualties.”

But the senior director for counterterrorism in former President Barack Obama’s National Security Council pushed back on any criticism the former president didn’t do enough to defeat ISIS.

“This was a top priority from the early days of ISIS gaining the type of territorial safe haven in particular, there was recognition that safe havens for terrorist groups can mean terrorist plots that extend — not just into the region — but to Europe and conceivably into the United States,” said Joshua Geltzer, author of “US Counter-Terrorism Strategy and al-Qaeda: Signalling and the Terrorist World-View,” now a visiting professor at Georgetown Law School.

The latest American intelligence assessment says fewer than 1,000 ISIS fighters now remain in Iraq and Syria, down from a peak of nearly 45,000 just two years ago. U.S. officials credit nearly 30,000 U.S.-led coalition airstrikes and regional partners on the ground for killing more than 70,000 jihadists. Meanwhile, only a few thousand have returned home.

The remaining ISIS strongholds are concentrated in a small area along the border of Syria and Iraq. ISIS, at one point, controlled an area the size of Ohio.

While ISIS has been largely defeated, it continues to call on followers around the world to conduct terror attacks during the holidays with a new message sprouting up on Tuesday, and a suicide attack in Kabul on Christmas with ISIS claiming responsibility. It’s part of the terror group’s effort to expand influence into Africa and Afghanistan. The U.S. envoy to the anti-ISIS coalition warned late last week not to expect a complete defeat anytime soon.

“ISIS became a brand, and a lot of pre-existing terrorist groups — you’ve seen this in the Sinai, for example — start to raise the flag of ISIS, mainly to recruit foreign fighters and other things,” said Brett McGurk, Special Presidential Envoy for the Global Coalition to Counter ISIS at the U.S. Department of State, in a press briefing Thursday with reporters at the State Department.

Deptula thinks the ISIS fight would have ended much sooner if then-President Obama had given his military commander in the field more authority. He compared President Obama’s actions to President Lyndon B. Johnson during the Vietnam War.

“Obama micromanaged the war,” Deptula said. “We could have accomplished our objectives through the use of overwhelming air power in three months not in three years.”

Deptula said ISIS-controlled oil supplies weren’t targeted for 15 months beginning in 2014, giving the terror group $800 million in much needed revenue to plot attacks and enslave millions of innocents.

In addition to ISIS, an old nemesis has taken root in Syria, and which might take on a bigger priority for the Trump administration next year, according to Geltzer.

“A lot of folks when they think about Al Qaeda probably still think of its center of gravity as being on that Afghanistan-Pakistan border,” he said. “But I would think of the center of gravity for Al Qaeda really having shifted to Syria at this point.”