Any cache of explosives, all collected in one place, makes a tempting target. For an attacker, the hard part is getting an explosive inside the building to set it off. Drones are the ideal mechanism for this mayhem. Relatively cheap and expendable, a drone's major limitation is how much weight it can carry. In this case, the aerial vehicle seems to have transported a Russian-made ZMG-1 thermite grenade.

Thermite hand grenades are light and potent. For example, the American military uses a thermite-based grenade similar to the ZMG-1. Describing the former, the U. S. Navy Small Arms and Special Warfare Ammunition manual says, “With imaginative use, the grenade can be an effective and versatile demolition tool.” According to the same manual, the American grenade can destroy oil drums, shipping containers...and metal ammunition boxes. Russia's ZMG-1 probably shares these abilities.

With light weapons like these, even hobbyist drones can transform into deadly weapons. As a result, stopping drone attacks has become an increasingly prominent problem for the militaries across the world. In Iraq, the violent nonstate actors ISIS built drones, booby-trapped those drones, and also used regular hobbyist drones as grenade-dropping mini-bombers. In the eastern Ukraine, as fighting continues between the Ukrainian government and Russia-backed separatists, both sides have fielded drones to scout trenches and even act as artillery spotters.

To counter this type of drone warfare, countries are investing in everything from eagles to lasers to special jamming rifles. There's no consensus yet on the best anti-drone tool—and until there is, it's unlikely that every ammunition depot will manage to protect itself against drone threats.

That doesn't mean Ukrainian military planners are helpless to prevent another explosion of this scale. When thermite detonates stockpiled bombs, the result is devastating—but it's a known military problem. Take this incident at the U.S. Bien Hoa airbase: In 1965, a jet set off an accidental explosion that resulted in 28 dead and 77 injured. In response, the Air Force rebuilt the base with revetments—which are thick, sturdy, blast-proof barriers—between each plane's parking space. That way, even if one plane exploded, it couldn't set the others on fire. And the U.S. military didn't stop there. After the disaster at Bien Hoa, the Air Force recognized how important it is to prevent catastrophic explosions within bases. They made revetments a standard part of military planning going forward.

Similarly, Ukrainian forces could treat this incident as a wake-up call. While they might still struggle to stop drones, they can improve the design of their armories with tools like revetments. Better structures and safety measures would mitigate the harm a single drone can do with a single grenade.

Watch the video of the explosion below: