Hand grenades are designed to be thrown, so they are light. But when they are dropped from drones, this can be a drawback. With a typical weight of just 300 grams, grenades are short on “killing power”, says a man nicknamed “Lyosha”, who is an amateur weapons-maker based in Kyiv. After one goes off, he says, targeted Russian soldiers “often just keep running”.

Three months ago Lyosha and a group of friends, working in their homes, designed an alternative: an 800-gram anti-personnel bomb called the “Zaychyk”, or “Rabbit”. The group uses 3D printing to produce the bomb’s casing, before sending it to be filled with C4, an explosive, and pieces of steel shrapnel. In tests, Lyosha says, this shrapnel cuts into wooden planks “like butter”.