When does the unthinkable become thinkable?  When tantrum-throwing children have in their possession the most destructive force on Earth.

North Korea and the U.S. exchanged bombastic threats on Tuesday, making it ever harder for the two sides to climb down from the ledge and find a peaceful way forward.

For the uninitiated, we're talking about nuclear war.  The threat is real.  The possibility is real.  Both President Trump and Kim Jong-un are painting themselves into a corner, where it is becoming less likely that one or the other can extricate himself without unleashing devastation upon the world.

In truth, it is Kim who must yield.  The U.S. cannot allow a paranoid, unstable regime to possess a weapon that can devastate American cities.  Some American intelligence officials believe that the North has already been able to marry a nuclear warhead to one of its ICBMs.  But there is no evidence that the warhead has been tested yet, leaving open the probability that the North is one step short of being able to hit the American mainland.

Can we take that chance?  Prudence demands that we don't.  But every time Trump ups his rhetorical attacks, Kim does the same.  And today, the North Korean military issued a statement saying it is targeting the U.S. territory of Guam.

Reuters:

North Korea said on Wednesday it is considering plans for a missile strike on the U.S. Pacific territory of Guam, just hours after President Donald Trump told the North that any threat to the United States would be met with "fire and fury".

The sharp increase in tensions rattled financial markets and prompted warnings from U.S. officials and analysts not to engage in rhetorical slanging matches with North Korea.

North Korea said it was "carefully examining" a plan to strike Guam, which is home to about 163,000 people and a U.S. military base that includes a submarine squadron, an airbase and a Coast Guard group.

A Korean People's Army spokesman said in a statement carried by state-run KCNA news agency the plan would be put into practice at any moment once leader Kim Jong Un makes a decision.

Guam Governor Eddie Calvo dismissed the threat and said the island was prepared for "any eventuality" with strategically placed defenses. He said he had been in touch with the White House and there was no change in the threat level.

"Guam is American soil ... We are not just a military installation," Calvo said in an online video message.

North Korea, which is pursuing missile and nuclear weapons programs in defiance of U.N. Security Council resolutions, also accused the United States of devising a "preventive war" and said in another statement that any plans to execute this would be met with an "all-out war wiping out all the strongholds of enemies, including the U.S. mainland".

Washington has warned it is ready to use force if needed to stop North Korea's ballistic missile and nuclear programs but that it prefers global diplomatic action, including sanctions. The U.N. Security Council unanimously imposed new sanctions on North Korea on Saturday.

Trump issued his strongest warning yet for North Korea in comments to reporters in New Jersey on Tuesday.

"North Korea best not make any more threats to the United States. They will be met with fire and fury like the world has never seen," Trump said.

One diplomat, Douglas Paal, who works for the Carnegie Endowment for Peace, had this to say about the president's rhetoric:

"It strikes me as an amateurish reflection of a belief that we should give as we get rhetorically. That might be satisfying at one level, but it takes us down into the mud that we should let Pyongyang enjoy alone," said Paal, who served as a White House official under previous Republican administrations.

There is something to be said for rhetoric that seeks to calm a dicey situation rather than make it worse.  Perhaps the president thought his explicit threat would cause Kim to pull back.  Instead, it appears to have had the opposite effect.  Within hours of the president's statement, the North issued its threat against Guam.

Kim is now well and truly trapped by his own rhetoric and his actions regarding nuclear and missile tests.  An attack on Guam would be suicide for North Korea.  But what may be driving Kim's rhetoric is the internal politics of the North Korean regime, not only rhetoric from Washington.

By almost all reports from recent North Korean defectors, Kim does not enjoy the kind of control over the regime that his father, Kim Jong-il, and grandfather, Kim Il-sung, exercised during their tenures at the top.  Any backtracking by Kim at this point could give his domestic enemies an opening to take him down.  While little is known of the inner workings of the regime, the cutthroat nature of politics there is well documented.  Purges under the younger Kim have been common, with gruesome means of execution to frighten dissenters.

Perhaps Kim is hoping China will intervene between the two sides.  They certainly have a lot to lose if war breaks out on the Korean peninsula.  Not only would refugees stream across their border, but the economic impact of another Korean war would devastate their economy (and the economy of the world). 

There is some indication that the regime is planning another missile test.  If the North Koreans go through with it, President Trump will have to decide whether to make good on his threats or look for another way out. 

Few are betting on a peaceful resolution to the crisis.