To fight the Islamic State terrorist group, Donald Trump would “bomb the s--- out of” their oil fields or “bomb the hell out of ISIS.” Or maybe neither of those things.

The GOP presidential nominee has called for “very few troops on the ground,” but also 20,000 to 30,000 troops. Or he might just let Russia handle the fighting.

He proposed banning all foreign Muslims from entering the United States until we “figure out what is going on” with terrorism. Or maybe just people from certain countries.

After two events last weekend — a bombing in New York that involved a suspect who praised the Islamic State and stabbings in Minnesota for which the Islamic State has claimed credit — Trump has revived his tough talk on obliterating the terrorist group — vowing to “utterly destroy ISIS.”

But for more than a year, Trump has declined to lay out a coherent strategy for doing so. Whenever pressed for specifics, Trump insists that he has a plan but says it must remain secret to avoid tipping off the enemy.

What Republican presidential candidate Donald Trump told supporters in Greenville, N.C., on Sept. 6, 2016, is raising questions about his "fool-proof" plan to defeat Islamic State militants. (Sarah Parnass/The Washington Post)

The scattered ideas that Trump has offered publicly have often been contradictory, impossible or even illegal — alarming many national security and foreign policy experts in both parties.

“I don’t think he has a well-thought-through position on anything,” said Eliot Cohen, a top State Department official during the George W. Bush administration who helped organize an anti-Trump open letter earlier this year. “I don’t think he’s read much, I don’t think he’s studied these issues. I think, like with so many other topics, he’s just emoting.”

Plans all over the map

The fight against the Islamic State and how it should be waged is certain to be one of the central issues at Monday’s presidential debate between Trump and Democratic candidate Hillary Clinton at Hofstra University, an event that will include a section focused on “securing America.”

For Trump, the Islamic State and its escalating attacks on the West have been a central focus of his rhetoric since the GOP primaries.

He has accused President Obama of ignoring or even sympathizing with the terrorists.

Trump also frequently talks as if the United States and its partners are doing nothing to combat the group, which has been severely weakened by thousands of coalition airstrikes and other operations over the past two years.

At a rally in Greenville, N.C., Sept. 6, Republican presidential nominee Donald Trump said that as president he would give his top generals 30 days to present him with a plan to defeat the Islamic State terrorist group. (The Washington Post)

“We are going to take a swift, strong action to protect the American people from radical Islamic terrorism,” Trump said in Ohio on Wednesday. “In recent days, terrorists have attacked in New York City, New Jersey and Minnesota. And it’s going to get worse — it’s going to get worse. If Hillary is president, it would be disaster. If Trump is president, you will be very, very happy.”

For months, Trump has skipped the usual foreign policy and national security briefings that are a traditional part of running for president, declaring at one point: “I know more about ISIS than the generals do. Believe me.”

Trump approaches terrorism as he approaches many issues, saying that Democrats and the establishment have messed up everything through their stupidity — he once referred to foreign policy experts as “eggheads” — and that a savvy businessman such as himself would use common sense to quickly fix the problem.

The GOP candidate has said that he would “bomb the hell out of those oil fields” controlled by the Islamic State in a bid to cut off the group’s wealth.

Sometimes Trump adds that he would seize the oil itself, which would both violate international law in stripping a country of its resources and take decades to accomplish, given the volume of crude.

Trump has also insisted that no civilians would be harmed in the destruction.

“I would bomb the s--- out of them,” Trump said of Islamic State-controlled oil fields at a rally last year in Iowa. “I would just bomb those suckers. And that’s right: I’d blow up the pipes, I’d blow up the refineries. I would blow up every single inch. There would be nothing left.”

In terms of troop presence in Iraq or Syria, Trump has been all over the map.

He said he wants to send “very few” troops to the Middle East, while also saying during a primary debate that he would be open to sending 20,000 to 30,000 soldiers.

At other times, Trump has said the fight against the Islamic State should be left to Russia, which is allied with Syrian President Bashar al-Assad, who is opposed by the United States.

When it comes to the treatment of suspected terrorists in general, Trump has said he would bring back waterboarding — which is widely considered torture and forbidden under U.S. and international law — and use other interrogation tactics that are “much worse” because “torture works.”

Trump has said that he would “take out” the relatives of suspected terrorists, also forbidden under international law.

At various times, Trump has proposed temporarily banning nearly all foreign Muslims from entering the United States or stopping immigration from countries with high rates of terrorism. He has promised to kick all Syrian refugees out of the United States and relocate them to a “safe zone” in their war-torn country that he would force the Gulf States to finance.

Trump has also said he would shut down parts of the Internet so that the Islamic State cannot recruit young Americans, an idea that he has yet to fully explain.

After a terrorist attack in France this summer, Trump said he would request war authorization from Congress — an unprecedented departure from long-standing practice for American military engagement that would grant the president sweeping powers not invoked since World War II.

Trump has also called for the United States to mobilize a NATO coalition against terrorists — which has already happened — even while calling the alliance obsolete and complaining about its cost.

Concerns by experts

Trump’s inconsistent approach to the Islamic State challenge has prompted a wave of Republican foreign policy experts — many of whom rarely weigh in during a presidential election — to sign letters and op-eds warning of the danger of a Trump presidency.

Last spring, Cohen and more than 100 other Republican national security experts signed a letter denouncing Trump’s candidacy and stating that his “vision of American influence and power in the world is wildly inconsistent and unmoored in principle.” Last month, 50 Republicans, including former top aides and Cabinet members for the George W. Bush administration, signed a letter saying that Trump would be “the most reckless president in American history” and that none of them would vote for him.

And last week, 75 retired career Foreign Service officers — including ambassadors and senior State Department officials under Republican and Democratic presidents — signed an open letter stating they would vote for Clinton, not Trump, whom they accused of being “ignorant of the complex nature of the challenges facing our country, from Russia to China to ISIS to nuclear proliferation to refugees to drugs.”

Trump has countered such missives with a letter signed by 88 former generals and admirals who argue that the United States needs “a long-overdue course correction in our national security posture and policy.”

They describe a military that has been hollowed by “a series of ill-considered and debilitating budget cuts, policy choices and combat operations.”

Trump is regularly joined on the campaign trail by Michael T. Flynn, a retired three-star general who was pushed out of his assignment as director of the Defense Intelligence Agency.

Flynn has embraced and promoted Trump’s aggressive positions, adding a much-needed seal of approval.

“Political correctness kills. It will cause death, and we can’t have that,” Flynn said on Fox News earlier this week. “I’m going to be very candid here. You don’t have a lot of people yelling ‘Jesus Christ!’ and putting a knife in somebody’s body or putting a knife in somebody’s head. This is a different enemy. It’s an enemy that we have not, frankly, understood in a couple administrations, and we definitely don’t understand them right now.”

‘Too great a risk for America’

Clinton, a former secretary of state under Obama, has proposed ways to intensify and expand the current fight against the Islamic State in Iraq and Syria short of sending U.S. combat forces, which she says would be shortsighted. Clinton speaks frequently of what she calls an “intelligence surge” that would seek to coordinate intelligence among several nations to better counter Islamic State recruitment and fundraising.

Her major departure from Obama’s current policy would be to add a “no-fly” zone in northern Syria, to shelter civilians, and to allow better access for aid and relief supplies. Such a zone would have to be enforced from the air, which appears far more complicated now, with Russian and U.S. planes both flying over Islamic State-controlled territory, than when Clinton first raised the idea months ago.

Robert Gates, who was secretary of defense under George W. Bush and Obama, wrote in an op-ed in the Wall Street Journal last week that neither Trump nor Clinton have detailed approaches to dealing with terrorism that are dramatically different from what Obama is already doing.

But he questioned Trump’s willingness to “walk away from the region and hope for the best,” and accused him of being “willfully ignorant about the rest of the world, about our military and its capabilities, and about government itself” and unwilling to listen to experts.

“The world we confront is too perilous and too complex to have as president a man who believes he, and he alone, has all the answers and has no need to listen to anyone,” Gates wrote. “In domestic affairs, there are many checks on what a president can do; in national security there are few constraints. A thin-skinned, temperamental, shoot-from-the-hip and lip, uninformed commander in chief is too great a risk for America.”

Karen DeYoung and Anne Gearan contributed to this report.