In political theory, it’s known as “issue ownership”: to be known to voters as the party that cares most about something, and is best at it.

National security has been the Republicans’ issue for most of the past six decades. They lost their hold because of the Iraq War debacle, but now — after the Paris attacks and growing concern about the Islamic State — will press their traditional advantage in the 2016 presidential campaign.

“It ought to be a golden opportunity for the Republicans to play to their strength,’’ says Roy Licklider, a Rutgers University expert on politics and terrorism.

To do so, however, the GOP and its eventual nominee must come to terms with one of the most fraught tactics — and words — in foreign policy: containment.

President Obama has been criticized for using the term to describe his achievements against ISIL in Syria and Iraq, though in a press conference last week he used stronger language, saying the group “must be destroyed.”

A war of ‘containment’

Jeb Bush and Hillary Clinton, among others, reject the term containment.

Clinton: “Our goal is not to deter or contain ISIS, but to defeat and destroy ISIS.” Bush: “The mission is to destroy ISIS – not to contain it.’’

“Containment’’ doesn’t have much of a ring to it. But it’s been U.S. policy against major foes since the middle of the Korean War, when Gen. Douglas MacArthur’s attempt to run the North Korean army out of North Korea provoked a devastating counter-attack by the Chinese.

It’s also been responsible for many foreign policy successes, including one of the greatest of the 20th century — the collapse, without a bullet being fired, of the Soviet Union.

‘Why not victory?’

Containment is intimately connected to the Republican franchise in national security, one which Western New England University historian John Baick calls “a foundation of our political culture.” It dates to the presidency of Dwight Eisenhower, the World War IIgeneral who beat Hitler.

Democrats who’ve practiced containment (like John F. Kennedy in the Cuban Missile Crisis) have generally fared well. Republicans who’ve argued against it (like Barry Goldwater, who asked “Why not victory?’’ and lost big in the 1964 presidential election) have not.

Some Republican presidents have advanced national security by practicing containment while calling it something else.

In the 1952 campaign, Eisenhower and his future secretary of State, John Foster Dulles, criticized President Truman’s strategy of containing the Soviet Union. Dulles wrote an article in Life magazine that demanded a bolder approach that would give the U.S. the initiative, and called for the “rollback’’ of Soviet gains in Eastern Europe.

But when the Hungarians revolted against their Soviet- dominated regime in 1956, Ike refused to intervene, and the rebellion was crushed. In eight years now recalled for their relative tranquility, he didn’t roll back the Iron Curtain one inch.

‘Mr. Gorbachev, tear down this wall!’

Ronald Reagan was known for his hatred of what he called the Soviet “Evil Empire,’’ voiced in his famous demand in Berlin in 1987: “Mr. Gorbachev, tear down this wall!’’ Conservatives still praise his refusal to accept the geopolitical status quo. But Reagan didn’t forcibly roll back the Soviets – he helped spend them into submission with an arms buildup they couldn’t afford to match.

Conversely, the American invasion of Iraq in 2003 was pure rollback. And after the war turned sour a few years later, the Republicans’ reputation as security experts was undercut by public disenchantment and by the party’s own division over “pre-emptive war” and “regime change.’’ John McCain, the 2008 GOP presidential nominee, paid the price.

Now, ISIL is a problem that would seem in the GOP’s wheelhouse. But Dante Scala, a University of New Hampshire political scientist, points out that a party can’t benefit from issue ownership unless the issue it owns is decisive at election time. Will that be terrorism a year from now?

In the 1992 election, for example, RepublicanPresident George H.W. Bush’s successful prosecution of the Gulf War almost two years earlier wasn’t enough to overcome voters’ concerns about the economy — an issue the Democrats traditionally own.

What’s more, containment — as practiced by Democrats or Republicans — may not be the best way to fight a non-state foe.

James Carafano, a national security specialist at the conservative Heritage Foundation, says Islamic State’s existence destabilizes the region and gives it a platform from which to plan and execute terror attacks elsewhere. Steadily increasing the pressure, he says, won’t vanquish an enemy that just keeps adjusting.

While no presidential candidate seems willing to endorse containment of ISIL, few are calling for full-blown, unilateral rollback, either.

Focus turns to refugees

For most GOP candidates, the primary focus has not even been ISIL per se, but on slowing or stopping Obama’s plan to admit Syrian refugees, on the theory that some might be terrorists. It’s a reflection of the very different political dynamics that now exist when challenging a sitting president on national security.

“There was a time when there were strong constraints about what a candidate could say during a crisis,” says Dan Schnur, who was McCain’s communications director in 2000 and now directs USC’s Unruh Institute of Politics. “Those constraints no longer exist.”

Which underscores one value of issue ownership: Voters’ trust on Election Day that a candidate or a party, whatever they’ve said in the campaign, will do the right thing once they’re in power.