The U.S. has launched another round of retaliatory strikes against the Islamic State in Syria following last month’s ambush that killed two U.S. soldiers and one American civilian interpreter in the country.

Officials from Denmark, Greenland and the United States met Thursday in Washington and will meet again next week to discuss a renewed push by the White House, which is considering a range of options, including using military force, to acquire the island.

Trump said Friday he is going to do “something on Greenland, whether they like it or not.”

If it’s not done “the easy way, we’re going to do it the hard way,” he said without elaborating what that could entail. In an interview Thursday, he told The New York Times that he wants to own Greenland because “ownership gives you things and elements that you can’t get from just signing a document.”

Danish Prime Minister Mette Frederiksen has warned that an American takeover of Greenland would mark the end of NATO, and Greenlanders say they don’t want to become part of the U.S.

This is a look at some of the ways the U.S. could take control of Greenland and the potential challenges.

Military action could alter global relations

Trump and his officials have indicated they want to control Greenland to enhance American security and explore business and mining deals. But Imran Bayoumi, an associate director at the Atlantic Council’s Scowcroft Center for Strategy and Security, said the sudden focus on Greenland is also the result of decades of neglect by several U.S. presidents towards Washington’s position in the Arctic.

The current fixation is partly down to “the realization we need to increase our presence in the Arctic, and we don’t yet have the right strategy or vision to do so,” he said.

If the U.S. took control of Greenland by force, it would plunge NATO into a crisis, possibly an existential one.

While Greenland is the largest island in the world, it has a population of around 57,000 and doesn’t have its own military. Defense is provided by Denmark, whose military is dwarfed by that of the U.S.

It’s unclear how the remaining members of NATO would respond if the U.S. decided to forcibly take control of the island or if they would come to Denmark’s aid.

“If the United States chooses to attack another NATO country militarily, then everything stops,” Frederiksen has said.

Trump said he needs control of the island to guarantee American security, citing the threat from Russian and Chinese ships in the region, but “it’s not true” said Lin Mortensgaard, an expert on the international politics of the Arctic at the Danish Institute for International Studies, or DIIS.

While there are probably Russian submarines — as there are across the Arctic region — there are no surface vessels, Mortensgaard said. China has research vessels in the Central Arctic Ocean, and while the Chinese and Russian militaries have done joint military exercises in the Arctic, they have taken place closer to Alaska, she said.

Bayoumi, of the Atlantic Council, said he doubted Trump would take control of Greenland by force because it’s unpopular with both Democratic and Republican lawmakers, and would likely “fundamentally alter” U.S. relationships with allies worldwide.

The U.S. already has access to Greenland under a 1951 defense agreement, and Denmark and Greenland would be “quite happy” to accommodate a beefed up American military presence, Mortensgaard said.

For that reason, “blowing up the NATO alliance” for something Trump has already, doesn’t make sense, said Ulrik Pram Gad, an expert on Greenland at DIIS.

Bilateral agreements may assist effort

U.S. Secretary of State Marco Rubio told a select group of U.S. lawmakers this week that it was the Republican administration’s intention to eventually purchase Greenland, as opposed to using military force. Danish and Greenlandic officials have previously said the island isn’t for sale.

It’s not clear how much buying the island could cost, or if the U.S. would be buying it from Denmark or Greenland.

Washington also could boost its military presence in Greenland “through cooperation and diplomacy,” without taking it over, Bayoumi said.

One option could be for the U.S. to get a veto over security decisions made by the Greenlandic government, as it has in islands in the Pacific Ocean, Gad said.

Palau, Micronesia and the Marshall Islands have a Compact of Free Association, or COFA, with the U.S.

That would give Washington the right to operate military bases and make decisions about the islands’ security in exchange for U.S. security guarantees and around $7 billion of yearly economic assistance, according to the Congressional Research Service.

It’s not clear how much that would improve upon Washington’s current security strategy. The U.S. already operates the remote Pituffik Space Base in northwestern Greenland, and can bring as many troops as it wants under existing agreements.

Influence operations expected to fail

Greenlandic politician Aaja Chemnitz told The Associated Press that Greenlanders want more rights, including independence, but don’t want to become part of the U.S.

Gad suggested influence operations to persuade Greenlanders to join the U.S. would likely fail. He said that is because the community on the island is small and the language is “inaccessible.”

Danish Foreign Minister Lars Løkke Rasmussen summoned the top U.S. official in Denmark in August to complain that “foreign actors” were seeking to influence the country’s future. Danish media reported that at least three people with connections to Trump carried out covert influence operations in Greenland.

Even if the U.S. managed to take control of Greenland, it would likely come with a large bill, Gad said. That’s because Greenlanders currently have Danish citizenship and access to the Danish welfare system, including free health care and schooling.

To match that, “Trump would have to build a welfare state for Greenlanders that he doesn’t want for his own citizens,” Gad said.

Disagreement unlikely to be resolved

Since 1945, the American military presence in Greenland has decreased from thousands of soldiers over 17 bases and installations to 200 at the remote Pituffik Space Base in the northwest of the island, Rasmussen said last year. The base supports missile warning, missile defense and space surveillance operations for the U.S. and NATO.

U.S. Vice President J.D. Vance told Fox News on Thursday that Denmark has neglected its missile defense obligations in Greenland, but Mortensgaard said that it makes “little sense to criticize Denmark,” because the main reason why the U.S. operates the Pituffik base in the north of the island is to provide early detection of missiles.

The best outcome for Denmark would be to update the defense agreement, which allows the U.S. to have a military presence on the island and have Trump sign it with a “gold-plated signature,” Gad said.

But he suggested that’s unlikely because Greenland is “handy” to the U.S president.

When Trump wants to change the news agenda — including distracting from domestic political problems — “he can just say the word ‘Greenland’ and this starts all over again,” Gad said.

The private deal for “Action Comics No. 1” was announced Friday. It eclipses the previous record price for a comic book, set last November when a copy of “Superman No. 1″ was at sold at auction for $9.12 million.

The Action Comics sale was negotiated by Manhattan-based Metropolis Collectibles/Comic Connect, which said the comic book’s owner and the buyer wished to remain anonymous.

The comic — which sold for 10 cents when it came out in 1938 — was an anthology of tales about mostly now little-known characters. But over a few panels, it told the origin story of Superman’s birth on a dying planet, his journey to Earth and his decision as an adult to “turn his titanic strength into channels that would benefit mankind.”

Its publication marked the beginning of the superhero genre. About 100 copies of Action Comics No. 1 are known to exist, according to Metropolis Collectibles/Comic Connect President Vincent Zurzolo.

“This is among the Holy Grail of comic books. Without Superman and his popularity, there would be no Batman or other superhero comic book legends,” Zurzolo said. “It’s importance in the comic book community shows with his deal, as it obliterates the previous record,” Zurzolo said.

The comic book was stolen from Cage’s Los Angeles home in 2000 but was recovered in 2011 when it was found by a man who had purchased the contents of an old storage locker in southern California. It eventually was returned to Cage, who had bought it in 1996 for $150,000. Six months after it was returned to him, he sold it at auction for $2.2 million.

Stephen Fishler, CEO of Metropolis Collectibles/Comic Connect, said the theft eventually played a big role in boosting the comic’s value.

“During that 11-year period (it was missing), it skyrocketed in value.,” Fishler said “The thief made Nicolas Cage a lot of money by stealing it.”

Fishler compared it to the theft of Mona Lisa, which was stolen from the Louvre museum in Paris in 1911.

“It was kept under the thief’s bed for two years,” Fishler noted. “The recovery of the painting made the Mona Lisa go from being just a great Da Vinci painting to a world icon — and that’s what Action No. 1 is — an icon of American pop culture.”