(CNN) Things have been tense on the Korean Peninsula and many North Korea watchers believe the situation is dangerous.

But it hasn't reached the brink yet , and that's likely because US President Donald Trump and North Korean leader Kim Jong Un and their respective advisers are aware of the immense cost of the Korean War, which started June 25, 1950.

"If this goes to a military solution, it is going to be tragic on an unbelievable scale," Defense Secretary James Mattis said at a news conference in May

The legacy of the war lives on in North Korea, where it's still used as a key piece of propaganda for the Kim regime. American fighter jets blanketed the country with about 625,000 tons of bombs on North Korea, killing 20% of the country's population, according to one estimate.

If the conflict reignited, it could be even more cataclysmic this time around with the specter of nuclear weapons looming.

"The threat of war on the peninsula -- major war or a limited war -- has been present off and on since the end of the Korean War," Adam Mount, a senior fellow at the Center for American Progress, told CNN. "Both the United States historically and also North Korea have proved that they can demonstrate restraint, de-escalate a crisis (and) step back from the brink of war ... They're both interested in avoiding a war that would be in nobody's interest."

Photos: Photos: Scenes from the Korean War Scenes from the Korean War – An American soldier comforts a comrade during the Korean War, circa 1950. Click through to see more scenes from the Korean War. Hide Caption 1 of 16 Photos: Photos: Scenes from the Korean War Scenes from the Korean War – A woman and child wander among debris in Pyongyang, North Korea, after an air raid by U.S. planes, circa 1950. The war began on June 25, 1950, when the North Korean People's Army crossed the 38th parallel and easily overwhelmed South Korean forces in a surprise attack. Hide Caption 2 of 16 Photos: Photos: Scenes from the Korean War Scenes from the Korean War – An American soldier walks around the rubble of Hamhung, North Korea, in an undated photo. On June 30, 1950, President Harry S. Truman ordered American troops into the fighting. Hide Caption 3 of 16 Photos: Photos: Scenes from the Korean War Scenes from the Korean War – North Korean leader Kim Il-Sung, left, signs a document in Seoul, South Korea, in an undated photo. The armistice ending the war was signed in July 1953, and its terms included the creation of the Demilitarized Zone. Hide Caption 4 of 16 Photos: Photos: Scenes from the Korean War Scenes from the Korean War – A U.S. Army chaplain prays by injured soldiers at a combat field hospital in August 1950. Hide Caption 5 of 16 Photos: Photos: Scenes from the Korean War Scenes from the Korean War – U.S. Marines attack Hagaru-ri, North Korea, in December 1950. Hide Caption 6 of 16 Photos: Photos: Scenes from the Korean War Scenes from the Korean War – An abandoned girl cries in the streets of Incheon, South Korea, in September 1950. Hide Caption 7 of 16 Photos: Photos: Scenes from the Korean War Scenes from the Korean War – An American soldier searches a foxhole for enemies in February 1951. Hide Caption 8 of 16 Photos: Photos: Scenes from the Korean War Scenes from the Korean War – Gen. Douglas MacArthur, center, head of the U.N. Command in the Korean War, and other military personnel observe shelling in Incheon from the USS Mount McKinley in September 1950. Hide Caption 9 of 16 Photos: Photos: Scenes from the Korean War Scenes from the Korean War – The 187th U.S. Airborne Regimental Combat Team conducts a practice jump in South Korea, circa 1951. Hide Caption 10 of 16 Photos: Photos: Scenes from the Korean War Scenes from the Korean War – North Korean prisoners of war make baskets on the floor of a storage barn at a prison, circa 1951. Hide Caption 11 of 16 Photos: Photos: Scenes from the Korean War Scenes from the Korean War – Marines use a flamethrower in April 1951. Hide Caption 12 of 16 Photos: Photos: Scenes from the Korean War Scenes from the Korean War – The USS Missouri bombards Chongjin, North Korea, circa May 1951. Hide Caption 13 of 16 Photos: Photos: Scenes from the Korean War Scenes from the Korean War – U.S. Marines duck for cover in a bunker as a shell explodes in April 1952. Hide Caption 14 of 16 Photos: Photos: Scenes from the Korean War Scenes from the Korean War – Actress Marilyn Monroe entertains troops, circa 1952. Hide Caption 15 of 16 Photos: Photos: Scenes from the Korean War Scenes from the Korean War – U.S. troops emerge from helicopters onto an open field, circa 1953. Hide Caption 16 of 16

The heart of Seoul

While the tense situation on the Korean Peninsula could escalate quickly, there are a handful of scenarios that could play out, ranging from something as calamitous as nuclear strike to small-scale artillery attacks that do not devolve into all-out war, which happened in 2010.

"Part of the difficulty of discussing something like this is there's a wide range of possible contingencies that vary widely in terms of the outlook in terms of how damaging they are," Mount said. "The challenge is to try to control escalation."

Nuclear strikes on those capitals would be catastrophic in terms of loss of life, but an attack using conventional weapons could kill tens of thousands of people too.

"Combat in another Korean War would take place in Seoul's crowded suburbs. While our war planners estimated that US and South Korean forces would contain the North Korean advance north of Seoul, the price of defense would be heavy," Ash Carter and William Perry, two former US defense secretaries, wrote in a 2002 op-ed in the Washington Post.

"Thousands of US troops and tens of thousands of South Korean troops would be killed, and millions of refugees would crowd the highways. North Korean losses would be even higher. The intensity of combat would be greater than any the world has witnessed since the last Korean War," the op-ed said.

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The concerns about a costly battle in Seoul remain today.

Roger Cavazos of the Nautilus Institute found in a 2012 study that there would be about 3,000 casualties in the first few minutes of a conventional North Korean artillery barrage focused on South Korean forces and 64,000 in the first day.

A surprise volley fired indiscriminately could kill nearly 30,000 civilians, the study found.

North Korea could also fire its ballistic missiles at US, South Korean and Japanese forces (or civilian populations) throughout the region.

North Korea is mismatched when it comes to military technology and capability, experts say. And it's believed that many of its armaments could be out of date or do not function properly, according to a 2016 five-part analysis on the North Korea threat from the geopolitical intelligence firm Stratfor.

Though North Korea's air force and navy pale in comparison to those of the United States, both pose a threat, according to Stratfor.

"Even without the nuclear threat, attacking North Korea guarantees massive destruction in return," the Stratfor analysis said.

Nuclear threat

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If full-scale war broke out, a primary concern for the US would be to eliminate North Korea's nuclear threat.

The US Air Force might use 24 F-22 tactical fighters -- which can carry two 450-kilogram (1,000 pounds) bombs -- and 10 B-2 bombers -- which can deploy massive bombs to reach underground bunkers -- to eliminate North Korea's nuclear infrastructure, according to Stratfor.

"Because of their unique properties, these expensive, stealthy platforms would form the backbone of any anti-nuclear operations," it said.

The United States would also rely on its Tomahawk cruise missiles, incredibly precise weapons that can be fired from sea hundreds of miles away from their target, though collateral damage would likely also be an issue.

"The US Navy (with enough time to prepare) can surreptitiously park two of its four Ohio-class cruise missile submarines off the North Korean coast," according to Stratfor. "When combined with destroyers and cruisers from the 7th Fleet already in the area, the United States could use more than 600 cruise missiles for the mission."

A crucial problem is intelligence -- it's not clear exactly how many nuclear weapons the reclusive communist state has or precisely where they are.

The United States has a tough time gathering that sort of information on North Korea; former CIA Director Michael Hayden has called North Korea the toughest intelligence target on the planet.

Without this information, the US could fail to completely eliminate North Korea's rapidly progressing nuclear threat in the first throes of a war, potentially unable to stop an attack on the US mainland.

"Before the end of President Trump's current term, the North Koreans will probably be able to reach Seattle with an indigenously produced nuclear weapon aboard an indigenously produced intercontinental ballistic missile," said Hayden.

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What comes after war

For South Korea, cost is an important factor.

"Younger generations that did not personally experience the Korean War and the initial division of the peninsula do not see the imperative for unification, particularly during an economic downturn," said Kuyoun Chung, a research fellow at the Korea Institute for National Unification.

Opinion polls conducted ahead of South Korea's recent presidential election found that most voters were worried about jobs and the economy more than the country's relationship with the north.

China also has geopolitical and economic interests at play.

A conventional war would likely lead to Kim's ouster if Beijing -- Pyongyang's only real ally -- did not intervene on North Korea's behalf.

It's believed North Korea's policy makers recognize this. Though they will engage in provocative actions like missile launches, they tread with some caution to avoid a military response from adversaries.

"At the end of the day, North Korea's top priority is regime security and regime survival. So it will take every measure possible to make sure that it does not cross any American red lines," said Tong Zhao, a fellow at the Carnegie-Tsinghua Center for Global Policy in Beijing.

Even if the US and South Korea were able to swiftly topple the Kim regime, there would be a series of complications in the aftermath of a war.

Pyongyang's nuclear material would likely be less secure and could fall into the wrong hands. Conflict could spark a refugee crisis. And a change in the region's balance of power could be followed by countries jockeying for more power, fueling instability.

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"The result of a North Korean regime collapse would be catastrophic and may trigger a dangerous race between China and the US-ROK (Republic of Korea) forces attempting to secure strategic and symbolic locations such as the Yongbyon nuclear facility and Pyongyang," Andrew Injoo Park and Kongdan Oh wrote for the National Bureau of Asian Research.

China worries about both of those, especially the latter.

Beijing values Pyongyang as a strategic buffer between itself and US-allied South Korea. If North Korea were to fall, it could lead to a US-allied unified Korea, with US troops right on China's border.