With little time to evacuate, millions of innocent citizens would be caught in the crossfire if the US and its regional allies were to initiate a first strike, that would almost certainly result in high casualties on both sides.
Friday morning, President Donald Trump warned on Twitter that "Military solutions are now fully in place, locked and loaded," though he said "hopefully Kim Jong Un will find another path!"
A military operation would consist of a swift and multi-dimensional attack, as the fight would be defined by the first minute of combat, according to Jerry Hendrix, a retired Navy captain and senior fellow at the Center for New American Security.
While Hendrix has not been briefed on the specifics of a possible preemptive strike option, he told CNN that the operation would likely include several strategies aimed to neutralize North Korea's defensive and counterstrike capabilities.
Countering North Korea's relatively formidable surface-to-air missile defense capabilities, stealth American F-22s, F-35s and B-2 bombers would likely lead a joint air campaign with the help of Japanese and South Korean F-15 or F-16 fighters, he said.
Unmanned aircraft could also be used to limit risk to pilots.
The US would likely move additional aircraft to the region in the event of an imminent strike, but also maintains two major air bases in South Korea -- Osan with F-16 fighters and A-10 "tank killers," and Kunsan with F-16s.
Heavy airpower can be called in from the Pacific island of Guam, through which the US rotates B-1, B-2 and B-52 bombers.
As US and allied aircraft take out priority targets from the sky, American warships would launch a barrage of Tomahawk missiles concentrated on North Korean missile sites, air defense systems and response corridors capable of launching a retaliatory nuclear weapon, Hendrix said.
The US Navy has 10 guided-missile cruisers and destroyers based in Japan. The ships are armed with Tomahawk missiles for offensive purposes and the Aegis missile defense system that could be used to intercept North Korean launches.
The US could use cyber attacks to disrupt Pyongyang's weapons programs -- though experts say that would only delay, rather than stop them.
Urgent efforts to take out priority targets like air defense systems, retaliatory missile launch sites and service facilities -- coupled with assumptions that the US-led offensive would be met with heavy resistance -- are likely to take a toll on the US' inventory of bombs and missiles, warned Hendrix.
"What is the plan to resupply?" he said.
The US would need to ensure it had enough bombs, missiles and electronic warfare planes to destroy or disable North Korea's air defenses before deploying its heavy bombers, likely B-1s stationed in Guam, needed to strike North Korea's fortified nuclear weapons sites, according to Carl Schuster, a former director of operations at the US Pacific Command's Joint Intelligence Center.
Within minutes of initiating the attack, US aircraft and artillery assets would also be forced to coordinate with allied forces to destroy the thousands of North Korean missile tubes pointed directly at the South Korean capital of Seoul.
And that would just be the beginning.
"The problem is not hitting North Korea, its what happens next," Joe Cirincione, president of the Ploughshare Fund, an organization working to stop nuclear proliferation, told CNN.
"You strike North Korea, they are going to strike back and they have a devastating conventional arsenal built up on the border that could lay waste to Seoul," he said. "Estimates are that hundreds of thousands of South Koreans would die in the first few hours of combat -- from artillery, from rockets, from short range missiles -- and if this war would escalate to the nuclear level, then you are looking at tens of millions of casualties and the destruction of the eleventh largest economy in the world."
"That's what you are going to roll the dice on," Cirincione added.
While launching a devastating preemptive strike against North Korea is almost unanimously considered a last resort for the US and analysts said there are currently no signs that the US is planning a first strike, the concept of preemptive military action is, at very least, being considered as an option.
Trump remains committed to keeping "all options on the table" amid tensions with Pyongyang.
Claims that Pyongyang is considering a missile strike near the US territory of Guam, coupled with Trump's warning that any further North Korean threats will be met with "fire and fury," have also fueled concerns of possible conflict.
The US would surely use military force in response to any North Korean strike against American or allied targets, but two US defense officials told CNN on Thursday that there are no signs of any imminent launch activity from the rogue state.
On Thursday, Republican Sen. Lindsay Graham told radio host Hugh Hewitt that he has discussed the issue of North Korea in great detail with Trump and could see a scenario where the US carries out a "preemptive action to enforce the policy of denial of capability to hit the homeland."
While all war game scenarios show the US winning a military confrontation, that victory could come at the cost of hundreds of thousands of deaths, mostly in South Korea where millions of innocent people -- and nearly 30,000 US troops -- are already in range of North Korea's current missile capabilities.
According to the International Institute for Strategic Studies, North Korea can field 21,000 artillery pieces. Many of those are within range of the 25 million South Koreans living in the Seoul metropolitan area.
"The scenario of a US preemptive strike is one that acknowledges our diplomacy has failed -- and our policy for last 25 years has failed," said Hendrix. "The only reason this would occur is if there is a calculation that concludes the long-term threat would result in more casualties than what would be suffered during a military operation."
But it is the job of Trump's top military commanders to prepare for the day they hope will never come.
While current and former military professionals are "repulsed" by the potentially catastrophic consequences of a full-scale military strike, Hendrix told CNN that "we imagine these scenarios all the time because what we fear more is an irrational actor with a nuclear weapon that can reach the US."
Defense Secretary James Mattis has consistently said that he prefers to resolve issues diplomatically but reminded Pyongyang on Wednesday that the "regime's actions will continue to be grossly overmatched by ours and would lose any arms race or conflict it initiates."
Anatomy of a preemptive strike
While the US and its allies regularly flex their joint military might in North Korea's backyard, the proposition of conducting a full-scale preemptive attack remains a uniquely complex and risky undertaking.
If Trump were to order the planning of such an operation, logistical preparations for a successful battlefield campaign against North Korea would take weeks or even months to put in place, according to analysts.
The first challenge would be ensure Japan and South Korea are completely integrated in any plan for military action, according to Hendrix.
"The US would also need to, at very least, inform China of any potential strike -- putting them in a position where they know military action and communicating the expectation that they have to stay out of it," he said.
Mark Hertling, a retired US Army general and CNN analyst, said the tens of thousands of US civilians, many of them military dependents, would first need to be evacuated from South Korea.
"When you see dependents beginning to leave South Korea and Japan, then you realize that North Korea is very close to crossing red lines," Sen. Graham said on Thursday.
The US would also need to add to its forces in the region in what Hertling called "a reinforcement of shooters." These would include US Navy ships and submarines armed with cruise missiles, plus Air Force bombers that could operate out of bases in Japan or Guam, he said.
"Some of these are in places in the region, but not enough to decapitate North Korea in terms of their artillery," Hertling said.
North Korea has thousands of conventional artillery pieces within range of the South Korean capital of Seoul. Studies have estimated South Korean casualties from artillery barrages to be in the tens of thousands on the first day of conflict.
According to Hertling and Hendrix, the US and its allies would need a couple of weeks of airstrikes to take out that artillery. And the US would need the planes, bombs, fuel and support personnel in place to carry out that campaign, they said, comparing it to the country's Desert Storm operation against Saddam Hussein's Iraq in 1991.
Hertling also said at least two US Navy aircraft carrier strike groups would need to be in the waters near Korea before any US attack.
Once the priority targets are neutralized, the US and its allies would have to keep up sustained operations for a fairly long period of time to maintain constant pressure on Pyongyang until all designated military targets are destroyed or the operation facilitates a change in regime or policy, according to Hendrix.
Ground forces could have a role to play in the next wave of the campaign. Experts say between 90,000 and 200,000 US troops would be needed to secure the nuclear sites in North Korea.
According to the Rand
Corporation and the Pentagon, North Korea has dozens of bases containing nuclear materials -- most of them deep underground -- meaning it could take time to locate and neutralize them.
And facing a North Korean military with an estimated one million troops, South Korea would likely be called upon to contribute a portion of its 500,000-troop standing army.
Ultimately, experts suggest that a military strike could set North Korea's missile and nuclear missile programs back a year or two, but note that any limited military action will yield little long-term strategic benefits.
"There is this sort of rational dictator theory going around Washington that we could strike him with a measured strike and warn Kim Jong Un that if he retaliated we would come back tenfold -- that idea is absurd," Cirincione said. "That completely underestimates Kim Jong Un's strongman image -- if he allows his country to be attacked by the United States, if he sits back and takes it, his days in office are numbered."
There is no military solution, there's only a negotiated one," he said.