Front-runner Donald Trump speaks at the Republican Jewish Coalition Presidential Forum in Washington on Dec. 3, 2015. (Susan Walsh/AP)

The mass shooting in San Bernardino, Calif., has triggered an avalanche of tough rhetoric from the 2016 GOP presidential field, but it has not cleared up the muddle of foreign-policy positions that, so far, have defined the race.

On an issue that has typically divided Republicans along the fault line of whether to intervene abroad, categorizing the candidates simply as hawks or doves is hard.

The San Bernardino shooting has exposed a homeland vulnerability — and given the GOP candidates a new, unanimous rallying cry. On Sunday, most of them inveighed with almost identical hostility against President Obama’s Oval Office address that evening, in which he promised to stick with his current strategy for defeating the Islamic State. That strategy, the Republicans said, is not working.

Nonetheless, the moment has not altered the Republicans’ deeper differences over such complex and politically fraught questions as: When should the United States intervene militarily abroad? If anything, some of those differences have been shown to be even sharper in recent days.

Sen. Marco Rubio (Fla.) is among the Republican presidential candidates who support direct U.S. engagement abroad. (Saul Loeb/AFP/Getty Images)

“It’s almost like we’re all on a highway and there are no lanes, and so the cars are all bumping against each other,” former Arkansas governor Mike Huckabee, who is making his second bid for the White House, said in an interview. “Today, it’s hard to say there is a position that is easily defined.”

A number of the leading GOP candidates remain advocates of muscular U.S. engagement abroad. But others — notably businessman Donald Trump and Sen. Ted Cruz (Tex.) — have combined tough talk about defeating the Islamic State with less-clearly defined particulars about how they would go about doing it.

Trump regularly promises to “bomb the sh--” out of the Islamic State — yet boasts of his reluctance to put troops on the ground in Syria. Cruz has hurled the term “neo-con” to describe the “invade-every-country-on-Earth” philosophy of the more hawkish Republican candidates, yet over the weekend, he promised to bomb the Islamic State “into oblivion.” (Trump also called Monday for a ban on Muslims entering the United States — an announcement that prompted rebukes from Republicans and Democrats.)

The Republican candidates who claim to represent the party’s mainstream, including former Florida governor Jeb Bush, New Jersey Gov. Chris Christie and Sen. Marco Rubio (Fla.), offer a variable and, in some cases, vague set of positions on how to engage internationally. All three have argued for American ground troops in the fight against the Islamic State, and all have blamed Obama for the new international aggressiveness of Russian President Vladi­mir Putin. Only Christie has proposed shooting down a Russian plane if it crosses an American-enforced no-fly zone.

In 2008, the first time Huckabee ran for president, one international issue — the Iraq War — dominated all others. The GOP candidates, with the exception of libertarian Ron Paul, were practically unanimous in their hawkishness. The party ended up nominating the most aggressive of them, Sen. John McCain (Ariz.).

In every election since the end of World War II, Republicans have picked as their standard-bearer a candidate who advocates an expansive view of the United States’ role in the world. When they have strayed from an establishment choice, as in the nominations of Barry Goldwater and Ronald Reagan, the result has been an even more hawkish candidate.

Whether that will be the pattern this time is hard to tell.

Sen. Ted Cruz (R-Tex.) recently promised to bomb the Islamic State “into oblivion.” (Susan Walsh/AP)

Libertarian-leaning Sen. Rand Paul (Ky.), like his father Ron Paul, is the most skeptical of foreign military intervention. That viewpoint often finds a voice in GOP primaries, but it does not prevail. The younger Paul’s candidacy is flagging.

Among the chief hawks, only Rubio is polling in the double digits.

Harder to peg is bombastic front-runner and foreign-policy novice Trump, whose poll numbers seem to rise every time terrorism stirs. His promise to “bomb the sh--” out of the Islamic State, also known as ISIS, is one of his most popular applause lines. But Trump also notes that he opposed the Iraq War at a time when virtually the entire Republican Party supported it.

“Trump has this fascinating dichotomy where, when he goes backwards in time, he sounds isolationist,” said Ari Fleischer, who was White House press secretary for George W. Bush. “When he goes forward in time, he’s going to bomb the blank out of them — you’ve never met a tougher guy. That resonates.”

But it does not suggest a coherent worldview, many observers say.

“His is more foreign policy by reflex, and it so far hasn’t hurt him,” said Peter Feaver, a Duke University political science professor who was a top national security official in the Bill Clinton and George W. Bush administrations.

Cruz, too, seems to have a foothold in various camps and rejects what he says is a “binary” choice, in which “we want to retreat from the world and be isolationist and leave everyone alone, or we’ve got to be these crazy neo-con invade-every-country-on-Earth and send our kids to die in the Middle East.”

Cruz also sided with Rand Paul in favoring an end to the National Security Agency’s program of bulk collection of telephone metadata, and he often jokes to crowds at his rallies that they should turn on their cellphones so Obama can listen in.

Colin Dueck, an associate professor of policy, government and international affairs at George Mason University, says that Trump and — increasingly — Cruz fit into a category he calls “conservative nationalists.”

They are not simply splitting the difference between isolationism and internationalism, he says, but they “have their own distinct approach, which includes, for example, an affection for foreign-policy sticks — the U.S. military — but not carrots — foreign aid, trade agreements, civilian capacity.”

“This is a potential problem,” he added. “Foreign policy must combine sticks with carrots in order to work.”

The candidates also face a host of new and complicated questions on national security.

Among them: whether to partner with Putin, an adversary elsewhere, on what appears to be mutual interest in eradicating the Islamic State. Another is whether Syria’s civil war is the United States’ fight as well, and whether this country has a national interest in getting rid of Syrian President Bashar al-Assad.

Huckabee said that he can see merit in the idea of working with Putin in Syria, where the Russian agenda overlaps with that of the United States — although Huckabee acknowledged that he is somewhat surprised to find himself arguing that position, given his overall mistrust of Russia’s leader.

Cruz, in an interview last month with Bloomberg News, said the United States has “no dog in the fight of the Syrian civil war.”

He denounced his more interventionist rival Rubio as being in the same camp as Obama and former secretary of state Hillary Clinton, the front-runner for the Democratic presidential nomination, in favoring “military adventurism that has had the effect of benefiting radical Islamic terrorists.”

“Senator Rubio emphatically supported Hillary Clinton in toppling [Muammar] Qaddafi in Libya. I think that made no sense,” Cruz told Bloomberg News.

Rubio fired back, making a clear reference to Cruz when he lamented that some in his party have tried “to derail the postwar consensus about America’s role in the world.”

“They will never call themselves isolationists, but that is exactly what they are,” Rubio said in a speech last week to the Republican Jewish Coalition Forum in Washington.

While the ominous turn of events in the world and Trump’s leading position in the Republican race have scrambled the contours of foreign policy for GOP presidential candidates, other forces also are at work.

“We Republicans are still kind of coming to terms with the Bush legacy,” which included both a massive expansion of government in the interest of domestic security and an expansive view of the U.S. role in the world, said Kori Schake, a research fellow at Stanford University’s conservative Hoover Institution who was a senior adviser to McCain’s 2008 presidential campaign.

“What we’re thrashing around for, is there another answer that is simpler, and less costly, and demands less of us?” Schake said.

In his Bloomberg News interview, Cruz spoke dismissively of “the Washington neo-cons,” a reference to the neoconservative philosophy of exerting U.S. power overseas to promote democracy and American values. Neoconservatism reached the peak of its influence during George W. Bush’s two presidential terms.

“I don’t remember any conservative ever calling other conservatives ‘neo-cons,’ which is of course in the post-Bush world a pejorative term, insinuating that the person is for all these sort of foreign-policy jaunts without any sort of circumspection,” said former senator Rick Santorum (R-Pa.), another presidential candidate, who touts his eight years of experience on the Senate Armed Services Committee.

Cruz’s backers, however, say that his position is closer to that of the majority of the Republican electorate.

“They are not allergic to foreign intervention — when you can make a very clear case,” said Victoria Coates, Cruz’s national security adviser. She added that while most voters see getting rid of the Islamic State as vital to U.S. interests, they do not feel that way about intervening in the Syrian civil war.

The practice of Cruz and Trump to talk tough while decrying the party’s hawks has frustrated some Republicans. Santorum suggested that a Cruz nomination would put Republicans “to the left of Hillary Clinton.”

In an interview, McCain worried that both men were distorting and distracting from a conversation that the party needs to have.

“When Lindsey Graham [the South Carolina senator who is also running for president] and I said that we had to arm the Free Syrian Army so that they could fight against the barrel-bombing and the slaughter, Sen. Cruz said that would be the air force for al-Qaeda,” McCain said. “I mean, totally disconnected from what we were trying to do.”

That the Republicans are having these arguments at all is a healthy development, George Mason University’s Dueck said.

“When a party loses a presidential election or two, you get a healthy debate over what do you stand for?” Dueck added. “In the end, how you settle it is to have a primary.”