Threatening to fire a volley of missiles toward a major US military hub _ and the home to 160,000 American civilians _ may seem like a pretty bad move for a country that is seriously outgunned and has an terrible lot to lose.
"Make sure you understand that this is not the final decision", Robert Carlin, the former chief of the Northeast Asia Division at the State Department's Bureau of Intelligence and Research, told reporters on a call organized by 38 North, a website that brings together experts on North Korea.
The five-minute drill begins with a siren on radio, and cars are stopped at designated spots.
The now deployed radar of the USA missile defense system THAAD only monitors missiles originating from the north, and South Korea's Green Pine radar warning system are not sufficient for tracking submarine-launched attacks at sea, according to the report.
"Things will happen to them like they never thought possible, OK?"
After Pyongyang conducted two successful tests of an intercontinental ballistic missile last month, putting much of the mainland United States within reach, the paper warned: "Trust in the nuclear umbrella the U.S. provides to the South can be shaken".
Called Ulchi-Freedom Guardian, the exercises are expected to run from August 21-31 and involve tens of thousands of American and South Korean troops on the ground and in the sea and air.
Chinese President Xi Jinping and other world leaders have called for calm as both Pyongyang and Washington upped their saber-rattling rhetoric. For years, North Korea has claimed Guam is within its missiles' striking distance, making furious statements each time when the USA flew powerful bombers from the island's air base to the Korean Peninsula.
The two leaders also reiterated a commitment to the denuclearization of the Korean Peninsula.
After Trump's "fire and fury" threat heightened tension, average daily sales volume has been 250 bars, ranging in weight between 10 grams (0.35 oz) and 100 grams (3.5 oz), versus about 50 earlier, Song said, adding the trend would continue through August.
French President Emmanuel Macron called for the worldwide community to work with North Korea to "resume the path of dialogue without conditions", following a call with Trump Saturday.
In a recent message, Seoul Mayor Park Won-soon said, "Since North Korea is very close to crossing the red line, Seoul needs to ramp up all defence measures against North Korea's potential threat", said another Seoul city official who asked not to be identified by name.
Such threats are why the Americans are on Guam to begin with.
"There's a lot of disbelief going on, there's a lot of anxiety", Father Paul Gofigan told CNN after the mass.
Its population is mostly Roman Catholic and about a third are Chamorro, descendants of the indigenous people Portuguese explorer Ferdinand Magellan first encountered in 1521.
"Faith is so deeply rooted into our culture", he said. We live on a small island. "About 162,000 people - mostly United States citizens - call the island home".
"Nobody really deserves to be caught in the middle of these games", said Victoria-Lola Leon Guerrero, an activist who campaigns for a lowered military presence.