A drumbeat of threats by North Korea over the years has fostered a sense of resilience among the island's 162,000 inhabitants.
A drumbeat of threats by North Korea over the years has fostered a sense of resilience among the island's 162,000 inhabitants, whose lives are deeply intertwined with the US military, which has 6,000 troops based there.
Guam Governor Eddie Calvo said the remote Pacific island was accustomed to being a target ever since Washington placed military installations there.
"We have to understand that even in a million-to-one scenario we have to be prepared with Guam being what it has been for decades, an American territory with strategic military assets in place in a very dynamic region."
"We are prepared for any eventuality, more so than any other American community," he said.
He did not elaborate on Guam's defences but the island houses two US military installations, and is also armed with a sophisticated weapons system known as THAAD, which can destroy short, medium and intermediate-range missiles in their final phase of flight.
"The way our infrastructure is built -- an 8.3 earthquake a decade ago, powerful typhoons -- they are well-equipped to coordinate both pre-event and also post-event," he said.
Hours earlier, as North Korea's war of words with US President Donald Trump intensified, Pyongyang said it was developing a plan to launch four intermediate-range missiles towards the Pacific island.
In Guam's capital Hagatna, residents were unruffled by Pyongyang's rhetoric.
"If it's going to happen it's going to happen," Loiue Joyce, a woman in her mid-20s, said of the North Korean threat, as she enjoyed a day of shopping.
"Scary? Yes, but what can we do? We live on a small island. There's really nowhere to hide if the attack were to happen."
A key US military stronghold, Guam was the departure point for US B-52 bombers that attacked Hanoi during the 1955-1975 Vietnam war.
In addition to the military presence, Guam also relies heavily on tourism to boost its economy, attracting more than 1.5 million visitors drawn to its pristine beaches and luxury resorts in 2016.
Authorities said the regional tensions had not dampened tourists' appetite for the island.
"It's business as usual in paradise," said Josh Tyquengco, marketing director at Guam Visitors Bureau, the official agency for the island.
"I am not aware of any cancellations. This is peak season for Guam. I don't see North Korea's story having any impact on tourism at this point."
But the Guam Daily Post said in an editorial that although the island's residents were used to North Korea's threats, the situation was more precarious today because "a feisty, not-so-cool-headed commander-in-chief lives in the White House now".
The last time Guam feared a North Korean attack, in 2013, tensions eventually simmered down because then US President Barack Obama's administration avoided a verbal war with North Korean leader Kim Jong Un, the newspaper said.
"This time, the North Korean threat is different, and more worrisome because North Korea's Guam-specific threat was reportedly in reaction to President Trump's statement saying: 'North Korea best not make any more threats to the United States. They will be met with fire and fury.'
"So now, the ball is back in Trump's court. The United States has been threatened via a direct threat to Guam, which isn't just a host for Air Force and Navy bases. About 162,000 people –- mostly US citizens –- call the island home."