This is a story about ICBMs, North Korea and an infamous bioweapon. But to get there, we need to take a quick detour through the historical memory of World War II. It’s a short detour, I promise.

Ask about the most terrifying weapons of WWII and people will likely respond with the atomic bomb. Then they’ll mention horrific crimes against prisoners, or perhaps the nightmarish spectre of kamikaze crashes. If they grew up with a strong memory of the blitz, they’ll speak of tanks and the terrifying whistle of dive bombers, or they’ll talk of months spent hiding underground while the war raged in the sky above. A particularly grim individual might mention the mass starvation across the world as fighting nations oriented everything to the war effort, leaving famines in their wake. Eventually, someone might mention the V-1, a proto-cruise missile, or the V-2, the first modern ballistic missile to see use in war.

Let’s consider the V-2 specifically. With a warhead carrying about 2,000 pounds of explosives, it is responsible for roughly 20,000 deaths, though a majority of those were people — largely forced concentration camp labor — killed in the production of the rocket, and not targets for the weapon. Four years prior, the Luftwaffe’s blitz over London killed 32,000 British civilians, and for simple reasons. If the goal of a military is mass casualties through conventional explosive, bombers are much more efficient vehicles than ballistic missiles.

The V-2 (and its inventor, scientist/war criminal Wernher von Braun) went on to influence the development of far more powerful rockets, and it was in the Cold War the ballistic missiles finally met their signature application: carrying thermonuclear warheads, with a punch measured in megatons. The great limitation with ballistic missiles was the relatively small amount of conventional explosives they could carry, especially when compared with bombers. A V-2 could level a house, or maybe a part of a city block if it hit right and the construction was shoddy. A nuclear warhead can level a city.

Intercontinental ballistic missiles became synonymous with nuclear peril, and nukes synonymous with ICBMs. In 2010, the United States even looked at replacing nuclear warheads on ICBMs with conventional warheads, but found the chief risk would be Russia assuming an ICBM carried a nuke, and then reacting as if it was a nuclear attack, instead of a conventional one. From the outside, there’s no good way to tell if an incoming ICBM is carrying megatons of thermonuclear death, or a less deadly payload.

All of which brings us to North Korea and a report from a Japanese paper citing an unidentified person connected to South Korea’s intelligence services. The report was picked up by Bloomberg, Vice and other outlets, and it suggests North Korea wants to test anthrax as the lethal payload for an ICBM.

Anthrax, by itself, is nasty, but it’s nasty in ways that make it unsuited for a ballistic missile warhead. Ballistic trajectories require the missile to travel through space and back to Earth, and if there’s any failing in the heat shield, then the anthrax itself will be rendered inert, as anthrax is sensitive to heat. It needs to find a pathway into open lesions, so when used as a deliberate attack on humans, it works better if placed where a person will inhale, rather than just blasted through the air. For these reasons, anthrax is a terror weapon that works better in envelopes than a weapon of war distributed by explosion. And, finally, it doesn’t really matter what the payload of an ICBM is; any country attacked by an ICBM will treat it as a nuclear weapon and respond accordingly.

It is a safe assumption that North Korea is devoting efforts on making sure its nuclear warheads can work when carried by ICBMs, and on making sure there are enough missile bodies to match the supply of warheads. Wasting a missile on a less effective munition, especially when everyone will respond to the missile launch as though it was a nuclear attack anyway, is cartoonishly inept at best.

If North Korea really wanted to launch an anthrax-filled rocket, it would be much better served revamping mail rockets, which were already designed to delivery envelopes. As for ICBMs, it’s safe to assume that any payload they carry will be nuclear, and not only that, it’d be folly to assume otherwise.