North Korea Is Threatening to Attack Guam. Why Guam?

North Korea’s announcement this week that it is preparing plans to fire four missiles near the U.S. Pacific territory of Guam has heightened the tensions between Kim Jong Un and President Donald Trump.

After Trump on Tuesday appeared to threaten nuclear war against North Korea by promising “fire and fury like the world has never seen,” Pyongyang responded Wednesday that it was “carefully examining the operational plan for making an enveloping fire at the areas around Guam,” according to Reuters.

As many Americans wade through the back-and-forth threats between the two nations, they may be wondering how exactly Guam ended up in the middle of this war of words. Here’s what you need to know about Guam, and why it’s under fire.

What is Guam?

A tiny island in the Pacific Ocean, Guam stretches 30 miles long, and is just 12 miles wide at its largest point.

The United States took Guam from Spain in 1898 during the Spanish-American War, and the island soon became an important U.S. military outpost. During World War II, the Japanese seized Guam after the attack on Pearl Harbor in 1941, but the U.S. took the island back in 1944.

Today, 163,000 people live on the island. People from Guam are U.S. citizens, but they have their own governor and cannot vote for president.

The U.S. military maintains a strong presence on the island, which helps them keep a close eye on North Korea. One-third of the island is owned by the U.S. military, according to the New York Times, including an anti-missile unit and large stockpiles of munitions.

Where is Guam?

Guam lies about 5,800 miles west of San Francisco and 1,600 miles east of Manila in the Pacific Ocean. That puts it about three-quarters of the way from Hawaii to the Philippines.

It is about 2,100 miles southeast of Pyongyang, according to the Times. And while this may sound like a long distance, that puts it within striking distance of missiles — and is part of why the island is such a prime location for the U.S. military.

Why is North Korea threatening Guam?

The threats from North Korea this week came after months of escalating tensions. Trump had talked about North Korea during the presidential election, and relations with the county have been discussed since he took office.

But more recently, North Korea tested two intercontinental ballistic missiles last month that U.S. intelligence said could hit American cities. When the United Nations — backed by the U.S. — imposed sanctions on North Korea over those tests, Pyongyang criticized the move and has used the sanctions to explain its increasingly aggressive behavior.

Trump’s “fire and fury” comments came after a Washington Post report that North Korea had built a miniaturized nuclear warhead. So when Trump threatened North Korea, the country was ready to retaliate with a threat against Guam.

This is not a new situation for Guam. Due to the heavy U.S. military presence there and its closer location than the U.S. mainland, North Korea has frequently threatened it in the past. In 2004, South Korean newspapers reported North Korea could hit Guam, according to NPR, and in 2013, Pyongyang reminded the U.S. that Andersen Air Force Base on the island was within its range.

For now, Guam’s Governor Eddie Baza Calvo has said there is “no threat” to his island. U.S. Secretary of State Rex Tillerson has also tried to calm fears about military action, saying “Americans should sleep well at night,” but Trump continued to give mixed messages on the situation Thursday, implying that he stood by his threat from earlier in the week.