Armed men in uniform identified by Syrian Democratic Forces as U .S. Special Operations troops ride in a pickup in the village of Fatisah in the northern Syrian province of Raqqa. (Delil Souleiman/AFP/Getty Images)

President Obama never liked the phrase “war on terror,” declared by his predecessor, George W. Bush, barely a week after the Sept. 11, 2001, attacks. Bush sometimes also likened the ensuing conflict to World War III.

Obama has a very different way with words. Although he, too, has spoken of “war” on occasion, he leans more toward the “series of persistent, targeted efforts to dismantle specific networks of violent extremists that threaten America” that he outlined in a 2013 speech.

But whatever the preferred rhetoric, and despite the constant U.S. military deployments in ground, air and sea combat against terrorist groups for the past 15 years, the fact remains that Congress — with sole constitutional power to declare war — has not done so.

Donald Trump says he will change that. Following Thursday’s terrorist massacre in Nice, France, the latest in a crescendo of attacks across the globe tied in one way or another to the Islamic State, the presumptive GOP nominee said that if he were president, he would ask Congress to pass its first formal declaration of war since World War II.

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“This is a war,” Trump told Fox News. “If you look at it, this is war coming from all different parts.” He would also, Trump said, mobilize NATO for the fight.

On the Democratic side, Hillary Clinton deflected the same question.“I think it’s clear we are at war with these terrorist groups and what they represent. . . . we have to look at all possible approaches,” she told CNN.

NATO needs to be strengthened, Clinton said on Fox, and any involvement by NATO allies should be American-led. While NATO is not formally participating in the international coalition fighting in Syria and Iraq, all 28 alliance countries are participants, under U.S. leadership.

Most legal scholars find a war declaration irrelevant. “Declaring war does not serve any real function under modern international law, and it is not required as a matter of U.S. constitutional practice in order to wage war,” said Duke University professor Curtis Bradley, co-director of the Center for International and Comparative Law. Wars that were not declared include those in Korea, Vietnam, the Persian Gulf and Iraq — as well as the many deployments of U.S. troops in between those conflicts.

Others think it would be counterproductive.

“We looked at this in the Bush administration” and rejected it despite some high-level advocates, said John B. Bellinger III, who served as legal adviser to both the National Security Council and the State Department.

Bellinger said he understands why some think a formal declaration by Congress would “show resolve and strength of purpose and seriousness” at a time when the world is “out of control,” as Trump put it after the Nice attack.

“You look at the World Trade Center,” Trump told Fox’s Bill O’Reilly. “You look at San Bernardino. You look at Paris — 130 people killed and so many injured in Paris from that attack. And you look at Orlando . . . unless we get strong and you, know, really strong and very, very smart leadership, it’s only going to get worse.”

But a formal declaration would “look silly,” Bellinger said. “We are using very robust military force against ISIS. . . . It looks feckless to be declaring war against an amorphous group, and to a certain extent buys into their crusader narrative.” The Islamic State is also referred to as ISIS, ISIL and Daesh.

Far from declaring war, Congress has not even been able to agree on a specific authorization for Obama to use military force against the Islamic State. It has refused to consider a proposal the White House sent to Capitol Hill 17 months ago after the bombing started in Iraq and Syria, or to come up with its own alternative.

Democrats want to narrow the president’s authority, while Republicans want to widen it. Most, with memories of the political price paid for votes in 2002 approving Bush’s ill-fated invasion of Iraq, have preferred to ignore the subject.

In the meantime, the rhetorical combat over what to call both the fight and the fighters — Obama’s preferred “violent extremists,” Trump’s “radical Islamic terrorists,” or Clinton’s “radical jihadists” — will not go away.

There is little argument, outside certain legal and left-leaning political circles, that Obama has the power to do everything he is now doing and more. Although Obama and his top aides once ridiculed Bush’s claim of authority to wage war on his own as commander in chief of the armed forces under Article II of the Constitution, they now regularly invoke it.

There has been no serious challenge to the administration’s justification for its counterterrorism operations around the world under international “self-defense” doctrines, its claimed legal authority for drone strikes “outside areas of active hostilities,” and its interpretation of global conventions governing combat and human rights.

In the absence of its desired congressional authorization against the Islamic State, the administration has also said — and lawmakers have not disputed — that its military actions are covered under the 2001 authority to strike al-Qaeda, passed in the days after the 9/11 attacks.

But with an expected increase in attacks like those in Nice, Istanbul, Orlando, San Bernardino, Calif., and Paris — either planned or inspired by the Islamic State — and the still-slow march toward anticipated offensives against militant headquarters in Raqqa, Syria, and Mosul, Iraq, “war” drums are likely to grow in volume.

The Obama administration and its military commanders have said that attacks on both cities are in the planning stages. They have emphasized the need to prepare the ground with “shaping” operations that include training and assisting local forces and reclaiming surrounding territory.

At the same time, targeted U.S. airstrikes have been systematically eliminating the Islamic State’s leadership. While Raqqa continues to be the inspirational and ideological center of Islamic State power in the region, many of the top militant leaders are thought to have gone to ground in the triangle of territory straddling Iraq and Syria that the group still firmly holds. It remains unclear what kind of command-and-control operation still exists in Raqqa, although many of the group’s foreign recruits are still thought to be there.

The administration has said that its relatively slow but steady strategy has substantially shrunk Islamic State territory in both countries. It has been loath to launch direct air attacks on either Raqqa or Mosul to avoid the large numbers of civilian casualties that would inevitably result, and until indigenous ground forces are ready to overtake and hold them. Planning for the offensives, particularly against Raqqa, is now likely to be further slowed by upheaval in neighboring Turkey — where much of U.S. air power in the region is based — in the wake of Friday’s unsuccessful coup attempt there.

Both Trump and Clinton have said they would strike Raqqa sooner and harder. After last month’s attack in Orlando, in which 49 people were killed by a lone-wolf shooter, a U.S. citizen with no apparent operational links to the Islamic State, Clinton called for “ramping up the air campaign.”

Trump, who last year said that as commander in chief he would authorize the use of nuclear weapons against the Islamic State in Raqqa, complained after Orlando that Obama was dragging his feet in attacking the Syrian city.

“We have to be furious for a short period of time, and we’re not doing it,” Trump said. Asked by a Fox News interviewer whether he advocated hitting Raqqa “right now,” he said, “We’re going to have to start thinking of something.”

Liz Sly in Irbil, Iraq, contributed to this report.