President Donald Trump’s first speech before the U.N. General Assembly included two major points about North Korea that left viewers feeling worried. Many headlines in the immediate aftermath of the speech have zeroed in on Trump’s threat to “totally destroy North Korea,” but his language about Kim Jong Un being a “Rocket Man” carries far more serious and worrying implications.

Trump’s threat of total destruction does sound belligerent and hyperbolic, but it was preceded by a few important words that bolster the effectiveness of the rhetoric as a deterrent threat. The full quote was, “The United States has great strength and patience, but if it is forced to defend itself or its allies, we will have no choice but to totally destroy North Korea.”

Good deterrent threats reference a specific action that the issuing country is trying to prevent and spell out the punishment if the target country does not heed the warning. In Trump’s U.N. speech, the destruction of North Korea will only happen if Kim Jong Un attacks the U.S. or its allies. Inversely, if North Korea does not attack the U.S. and its allies then it will not be destroyed.

Importantly, the deterrent threat in Trump’s U.N. General Assembly speech is markedly better than his infamous “fire and fury” comment he made in early August. “Fire and fury” was a terrible deterrent threat because it was not clearly tied to an action the U.S. was trying to deter. Trump said, “North Korea best not make any more threats to the United States,” but what kind of threats was he talking about? Do bombastic military threats count? What about tests of ballistic missiles or nuclear weapons? Without a reference to a specific North Korean action that Trump wanted to prevent made the “fire and fury” threat little more than hot air.

Moreover, past presidents have made similar statements threatening military action against North Korea if it attacked the United States or its allies. For example, in a 2014 visit to U.S. troops stationed in South Korea, then-president Barack Obama said, “[The United States] will not hesitate to use our military might to defend our allies and our way of life” from a North Korean attack. After North Korea’s first nuclear test in 2006, George W. Bush stated, “[The United States] will continue to protect ourselves and our interests … [and] will meet the full range of our deterrent and security commitments.”

Trump’s threat to “totally destroy” North Korea in response to an attack uses more aggressive rhetoric than his predecessors, but the underlying logic (if you attack us, we will respond with overwhelming force) is consistent.

While “total destruction” is an improvement from “fire and fury,” Trump’s decision to call Kim Jong Un a “Rocket Man … on a suicide mission” should raise alarms about how he and his administration will deal with North Korea. Suicidal leaders are irrational. They cannot be bargained with, and they cannot be deterred. If Kim is indeed suicidal, then there is no point in negotiating with him. And if U.S. policymakers truly view Kim as such, offensive military action is the only effective option for stopping his behavior.

Kim Jong Un is undoubtedly a brutal and abhorrent dictator, but he is not irrational. When one looks past the perennial bombast of North Korea’s official statements, a very rational nuclear strategy comes into focus. Kim does threaten to use nuclear weapons first in a conflict, but only if he thinks the U.S. is preparing to carry out an attack. There is little chance for North Korea to win a war once it starts given the conventional and nuclear advantages of the United States, so Kim needs to prevent the war from starting in the first place.

The best option for preventing a U.S. attack is to threaten to escalate a conflict to nuclear war as quickly as possible, making the costs of military action prohibitively high for the U.S. This nuclear strategy can lead to very dangerous crises, but it is not suicidal or irrational for a weaker country to threaten rapid escalation in a bid to deter war.

The Trump administration will likely continue to ratchet up pressure on North Korea in the months to come, especially if the North conducts more ballistic missile or nuclear tests. If the administration truly sees Kim Jong Un as an irrational, suicidal “Rocket Man” and tougher sanctions fail to change his behavior, then pressure to take military action will grow. Hopefully Trump’s name-calling is more bullying than policy.