Washington (CNN) It's the no-win situation that can only be imagined by US military officials tasked with preparing for a worst-case scenario -- conducting a preemptive strike on North Korea.

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.

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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.

US B-1B Lancer bomber Engines: four turbofans with afterburner Wingspan: 137 feet (41.8 meters) extended forward, 79 feet (24.1 meters) swept aft Length: 146 feet (44.5 meters) Height: 34 feet (10.4 meters) Weight: 95 tons (86,183 kilograms) Speed: 900-plus mph Ceiling: more than 30,000 feet (9,144 meters) Payload: 37.5 tons (34,019 kilograms) Weapons: Joint Direct Attack Munitions. JDAMs are tail sections with GPS navigation capabilities that are attached to 2,000-, 1,000- and 500-pound bombs. Source: US Air Force

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.

Rising tensions

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.

China and North Korea China is North Korea's primary ally and trading partner

Trade between the countries was worth $2.6B in the first half of 2017

China has supported stringent UN sanctions against the North Korea

But experts say Beijing fears instability in North Korea more than anything

The collapse of Kim Jong Un's regime could lead to a flood of refugees into China

While a unified Korea -- ruled from Seoul -- could mean US troops on China's border

"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.

Photos: Photos: F/A-18 Hornets fly above the Nimitz-class aircraft carrier USS John C. Stennis in the Pacific Ocean. The US Navy has 10 of the 97,000-ton ships, which can carry more than 60 aircraft each. Hide Caption 1 of 10 Photos: An F-35B Joint Strike Fighter tests its vertical landing capability in 2015. The fifth-generation jets have been deployed to Marine Corps Air Station Iwakuni in Japan as the US moves some of its most modern equipment to Northeast Asia. Hide Caption 2 of 10 Photos: Chinese J-20 stealth fighters perform during the 11th China International Aviation and Aerospace Exhibition, also known as Airshow China 2016, in Zhuhai on November 1, 2016. The J-20 is one of China's answers to US F-22 and F-35 stealth fighters. Hide Caption 3 of 10 Photos: Chinese military vehicles carrying DF-26 ballistic missiles participate in a military parade at Tiananmen Square in Beijing in 2015. The missile has been dubbed "the Guam killer" by analysts for their ability to hit the strategic US island in the Pacific. Hide Caption 4 of 10 Photos: Korean People's Army (KPA) soldiers march on Kim Il Sung sqaure during a military parade in Pyongyang on April 15, 2017. North Korea trails only China, the US and India in the number of people in the military. Hide Caption 5 of 10 Photos: A North Korean tank participates in a competition in this 2017 picture released from North Korea's official Korean Central News Agency. North Korea has 3,500 main battle tanks in its arsenal. Hide Caption 6 of 10 Photos: The South Korean Navy's first Aegis destroyer "King Sejong" is seen at the launching ceremony at the Ulsan dockyard of Hyundai Heavy Industries in the southeastern port city of Ulsan in 2007. The 7,600-ton destroyer is considered by analysts to be among the world's most advanced warships. Hide Caption 7 of 10 Photos: A South Korean K2 tank (C) moves during an equipment demonstration at the Defense Expo Korea 2016 at KINTEX exhibition hall in Goyang, north of Seoul, on September 10, 2016. The K2, nicknamed the "Black Panther" is considered to be among the world's best tanks. Hide Caption 8 of 10 Photos: The Japanese submarine Oyashio, escorted by a Japanese destroyer, arrives at the former US naval base in Subic Bay, Philippines, in April 2016. Submarines are considered a key strength of one of the world's strongest navies. Hide Caption 9 of 10 Photos: Japan's Maritime Self-Defense Force helicopter destroyer Izumo takes part in a fleet review off Sagami Bay in October 2015. Helicopter destroyers combine with Japanese subs to give Tokyo exceptional anti-submarine warfare capabilities. Hide Caption 10 of 10

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.

Photos: In the U.S. Air Force fleet B-52 Stratofortress – The first versions of this long-range heavy bomber flew in 1954. A total of 744 were built, the last of those in 1962. The Air Force maintains 58 B-52s in the active force and 18 in the Reserve. A single B-52 can carry 70,000 pounds of mixed munitions, including bombs, missiles and mines. The eight-engine jets have a range of 8,800 miles. Hide Caption 1 of 24 Photos: In the U.S. Air Force fleet C-130 Hercules transport – A C-130J Super Hercules from the 37th Airlift Squadron flies over Normandy, France, June 3, 2015. First delivered to the Air Force in 1956, the C-130 remains one of the service's most important airlift platforms. More than 140 are still in active units, with more than 180 in the National Guard and a hundred more in the Reserve. The C-130 is powered by four turboprop engines. Hide Caption 2 of 24 Photos: In the U.S. Air Force fleet AC-130 gunships – The AC-130H Spectre and the AC-130U Spooky gunships are designed for close air support, air interdiction and force protection. Armaments on the Spectre include 40mm and 105mm cannons. The Spooky adds a 25mm Gatling gun. Hide Caption 3 of 24 Photos: In the U.S. Air Force fleet F-22 Raptor – The twin-engine F-22 stealth fighter, flown by a single pilot and armed with a 20mm cannon, heat-seeking missiles, radar-guided missiles and radar-guided bombs, can perform both air-to-air and air-to-ground missions. The service has 183 of the Raptors, which went operational in 2005. Hide Caption 4 of 24 Photos: In the U.S. Air Force fleet The single-engine F-35A is the Air Force's eventual replacement for the F-16 and the A-10. The supersonic jets, which will be able to conduct air-to-air and air-to-ground attacks, are just beginning to enter the Air Force fleet. Here, an F-35 Lightning II from the 34th Fighter Squadron at Hill Air Force Base, Utah, flys at Royal Air Force Lakenheath, England, April 15, 2017. Hide Caption 5 of 24 Photos: In the U.S. Air Force fleet B-2 Spirit bomber – The four-engine B-2 heavy bomber has stealth properties that make it hard to detect on radar. Flown by a crew of two, it has an unrefueled range of 6,000 miles and can deliver both conventional and nuclear bombs. Twenty B-2s are in the active inventory. They joined the fleet in 1997. Hide Caption 6 of 24 Photos: In the U.S. Air Force fleet B-1B Lancer bomber – The four-engine jet can fly at 900 mph and carry the largest payload of bombs and missiles in the Air Force inventory. The Air Force has 62 B-1Bs in the fleet. Hide Caption 7 of 24 Photos: In the U.S. Air Force fleet F-15 Eagle – The F-15 Eagle, the Air Force's main air superiority fighter, became operational in 1975. With a crew of one or two, depending on the model, the twin-engine jets are armed with a 20mm cannon along with Sidewinder or AMRAAM missiles. The Air Force lists 249 F-15 Eagles in its inventory. Hide Caption 8 of 24 Photos: In the U.S. Air Force fleet F-15E Strike Eagle – The Strike Eagle is a version of the air superiority fighter adapted to perform ground-strike missions. With a crew of two, the twin-jet can carry and deploy most weapons in the Air Force inventory and operate in any weather. The F-15E was first delivered in 1988. The Air Force lists 219 in its fleet. Hide Caption 9 of 24 Photos: In the U.S. Air Force fleet A-10 Thunderbolt – The A-10 Thunderbolt jets, nicknamed "Warthogs," are specially designed for close air support of ground forces. Key to their armaments is a 30mm Gatling gun. The pilot is protected from ground fire by titanium armor, and the plane's fuel cells are self-sealing in case of puncture. Hide Caption 10 of 24 Photos: In the U.S. Air Force fleet RC-135U – The RC-135U Combat Sent, based at Offutt Air Force Base, Nebraska, provides strategic electronic reconnaissance information to the president, secretary of defense, Department of Defense leaders and theater commanders. Hide Caption 11 of 24 Photos: In the U.S. Air Force fleet An F-15 Eagle takes off from the Andersen Air Force Base, Guam, flight line as two E-3 Sentries are seen in the background. Hide Caption 12 of 24 Photos: In the U.S. Air Force fleet OV-10 Bronco – A 21st Tactical Air Support Squadron OV-10 Bronco aircraft fires white phosphorus rockets to mark a target for an air strike during tactical air control training. Hide Caption 13 of 24 Photos: In the U.S. Air Force fleet A-29 Super Tucano – An A-29 Super Tucano taxis on the flightline during its first arrival, Sept. 26, 2014, at Moody Air Force Base, Georgia. Afghan Air Force pilots trained on the planes that will be used in air-to-ground attack missions in Afghanistan. Hide Caption 14 of 24 Photos: In the U.S. Air Force fleet KC-135 Stratotanker – The four-engine KC-135 joined the Air Force fleet in 1956 as both a tanker and cargo jet. It can carry up to 200,000 pounds of fuel and 83,000 pounds of cargo and passengers in a deck above the refueling system. More than 400 of the KC-135s are flown by active, Air Guard and Reserve units. Hide Caption 15 of 24 Photos: In the U.S. Air Force fleet F-16 Fighting Falcon – The single-engine jet is a mainstay of the Air Force combat fleet. It can perform both air-to-air and air-to-ground missions with its 20mm cannon and ability to carry missiles and bombs on external pods. More than 1,000 F-16s are in the Air Force inventory. Hide Caption 16 of 24 Photos: In the U.S. Air Force fleet C-17 Globemaster transport – The four-engine jet joined the Air Force fleet in 1993 with a primary mission of troop and cargo transport. Each plane can carry up to 102 troops or 170,900 pounds of cargo. The Air Force has 187 C-17s on active duty, 12 in the Air National Guard and 14 in the Reserve. Hide Caption 17 of 24 Photos: In the U.S. Air Force fleet C-5 Galaxy transport – The C-5, with a wingspan of 222 feet, a length of 247 feet and a height of 65 feet, is the largest plane in the Air Force inventory and one of the largest aircraft in the world. The first versions of the four-engine jet joined the force in 1970. The Air Force expects to have 52 versions of the latest model, the C-5M, in the fleet by 2017. Hide Caption 18 of 24 Photos: In the U.S. Air Force fleet CV-22 Osprey – The Osprey is a tiltrotor aircraft that combines vertical takeoff, hover and landing qualities of a helicopter with the normal flight characteristics of a turboprop aircraft, according to the Air Force. It is used to move troops in and out of operations as well as resupply units in the field. The Air Force has 33 Ospreys in inventory. Hide Caption 19 of 24 Photos: In the U.S. Air Force fleet E-3 Sentry AWACS – AWACS stands for airborne warning and control system. This four-engine jet, based on a Boeing 707 platform, monitors and manages battle space with its huge rotating radar dome. The planes have a flight crew of four supporting 13 to 19 specialists and controllers giving direction to units around the battle space. The Air Force has 32 E-3s in inventory. Hide Caption 20 of 24 Photos: In the U.S. Air Force fleet KC-10 Extender – Based on the DC-10 passenger jet, the triple-engine KC-10 is a gas station in the sky with the ability to carry 75 people and 170,000 pounds of cargo. In its six tanks, the KC-10 can carry up to 356,000 pounds of fuel and dispense it while airborne. The Air Force has 59 KC-10s on active duty. Hide Caption 21 of 24 Photos: In the U.S. Air Force fleet T-38 Talon – The twin-engine jet trainer, used by the Air Force to prepare pilots for the F-15E Strike Eagle, F-15C Eagle, F-16 Fighting Falcon, B-1B Lancer, A-10 Thunderbolt and F-22 Raptor, first flew in 1959. Almost 550 are in the active force. Hide Caption 22 of 24 Photos: In the U.S. Air Force fleet U-2 – The single-engine, single-pilot U-2 is used for high-altitude reconnaissance and surveillance. Flying at altitudes around 70,000 feet, pilots must wear pressure suits like those worn by astronauts. The first U-2 was flown in 1955. The planes were used on missions over the Soviet Union during the Cold War, flying too high to be reached by any adversary. The Air Force has 33 U-2s in its active inventory. Hide Caption 23 of 24 Photos: In the U.S. Air Force fleet WC-135 Constant Phoenix – The four-engine WC-135 is used to fly through airspace to detect the residue of nuclear blasts. "The aircraft is equipped with external flow-through devices to collect particulates on filter paper and a compressor system for whole air samples collected in holding spheres," the Air Force says. It has two of these jets in the active force. Hide Caption 24 of 24

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.