Vice President JD Vance accused the government of Denmark of “underinvesting” in Greenland while he was making a visit to an American military base on Friday in the Danish territory, which President Trump has repeatedly insisted should become part of the United States.

“Our message to Denmark is very simple: You have not done a good job by the people of Greenland,” he said.

Vance had traveled to Greenland along with his wife, Usha Vance, and a delegation of high-ranking Trump administration officials, including national security adviser Mike Waltz.

Usha Vance initially announced that she would travel to the island without her husband, but he joined the trip a few days later. The itinerary for the visit was also revised amid backlash from Greenlandic and Danish officials, including Múte Egede, Greenland’s former prime minister, who warned against “American aggression” after the trip was announced.

“We must … face the seriousness of the situation and acknowledge that every minute counts, to ensure that the Americans’ dream of annexing our country does not become a reality,” Egede told a local newspaper on Sunday.

Since returning to the White House, Trump has set his sights on annexing Greenland.

“We need Greenland,” he said on Friday. “It’s not a question of, ‘Do you think we can do without it?’ We can’t.”

For now, Greenland belongs to Denmark. Although the island was treated as a colony for hundreds of years, its citizens have had authority over what happens within its borders since the late 1970s. That freedom includes the power to decide whether it wants to remain a part of Denmark, join the U.S. or become an independent nation.

Trump first floated the concept of acquiring Greenland during his first presidential term, but there has been much more sustained focus on the concept since he returned to the White House in January.

His joint address to Congress earlier this month included a message “for the incredible people of Greenland” in which he said he strongly supports their “right to determine your own future.” But about 20 seconds later, he said he thinks the U.S. will acquire the territory “one way or another.” Earlier this year, he refused to rule out taking Greenland by force.

For their part, Greenlanders appear to have little interest in joining the U.S. voluntarily. Polls show that 85% of the island’s citizens oppose the idea, and nearly half of them see Trump’s interest in Greenland “as a threat.”

Egede has bluntly stated, “We don’t want to be Americans.” The island has new leadership, but its position on U.S. annexation won’t change. Jens-Frederik Nielsen, who was sworn in as Greenland’s new leader on Friday, is seeking a different path for his country.

“We want to be Greenlanders, and we want our own independence in the future,” he said earlier this month.

Greenland is not a major economic power, nor does it have a strong military to bolster U.S. forces. Its population is tiny and would clearly not welcome American ownership with open arms. So why does Trump want it so badly, to the point where he’s floated military action against a NATO ally to get it?

For one thing, it’s huge

While many maps tend to exaggerate Greenland’s size, it’s still massive — at 836,330 square miles, it’s more than three times the size of Texas.

It’s considered to be the world’s largest island and, on its own, would be the 12th-largest nation on Earth. It is also the least densely populated territory on the planet. More than 80% of its 56,000 residents occupy about a dozen towns along its coast; its vast, icy interior is essentially uninhabited.

Adding Greenland would allow the U.S. to leapfrog Canada and become the second-largest country in the world — although it would still be a distant second to Russia.

Location, location, location

Not only is Greenland big, it’s also in a highly strategic area. Key sea routes that connect Northern Europe to North America run along its coastline, making it a critical location for managing both international shipping and military power in the Arctic.

The fabled Northwest Passage to the northern edge of Canada and the Arctic Bridge route, which connects Scandinavia and Russia to North America’s East Coast, both hug Greenland’s southern tip.

Greenland is also home to an American military missile defense base located far north of the Arctic Circle, a prime position to monitor — or potentially intercept — any Russian rockets headed toward the U.S. mainland.

Because of climate change, which has made many areas of the Arctic impossible to navigate due to melting ice, Greenland’s position will only become more important. Within the next 25 years, experts predict that enough ice will melt to open up the Transpolar Sea Route, a shipping lane that would cut straight across the North Pole and create a more efficient path between Asia and the Atlantic.

The U.S. and its allies are already jockeying with Russia and, to a certain extent, China, over control of this swiftly evolving area of the globe. Owning Greenland would give the U.S. an enormous advantage in this geopolitical tug-of-war.

It’s changing

Like the sea ice that surrounds it, the ice that blankets Greenland’s vast interior is also melting. Nearly 2,000 square miles’ worth of ice has disappeared from the island’s surface over the past four decades. NASA refers to Greenland as a “canary in a coal mine” for climate change.

Greenland’s melting ice is one the biggest drivers of global sea level rise. It’s also causing a key ocean current known as the “great global ocean conveyor belt” to slow down, which could have huge implications for weather around the world.

But where climate experts see reasons to worry about Greenland’s ice melt, others see opportunity. That’s because Greenland is home to huge yet largely untapped stores of rare earth minerals needed to make a wide range of high-tech products — everything from smartphones to computers to fighter jets to green energy technologies.

The U.S. used to be the world’s top producer of rare earth minerals. That title today goes to China. To counter China’s dominance, U.S. leaders have moved to increase the United States’ own mineral mining, while also working to open up foreign sources for the materials. Greenland’s receding ice could set off a mineral “gold rush,” as large deposits of high-value minerals become accessible for the first time.

Greenland currently puts strict limits on mining within its territory and has banned oil and gas extraction entirely over environmental concerns. Full command of the island could give the U.S. the power to roll back those restrictions, make larger swaths of the island available for development and seize a larger share of the profits that result.

Many Greenlanders see a ramped-up mining industry as a key to their economic future, but even local support might not be enough to turn the dream of a mineral windfall into a reality. Foreigners have been coming to Greenland seeking to extract its riches for centuries, only to be turned away by its harsh terrain and brutal climate. Some experts believe that even with modern technology, tapping Greenland’s mineral resources may be too difficult and expensive to make large-scale mining economically viable.