The thermobaric weapon, also known as an aerosol bomb or fuel air explosive, is a two-stage munition.

The first-stage charge distributes an aerosol made up of very fine material – from a carbon-based fuel to tiny metal particles. A second charge ignites that cloud, creating a fireball, a huge shock wave, and a vacuum as it sucks up all surrounding oxygen.

The blast wave can last for significantly longer than a conventional explosive and is capable of vaporising human bodies.

Such weapons are used for a variety of purposes and come in a range of sizes. Hellyer says what we may see in Ukraine is Russia using them in a “bunker-buster” role to destroy defensive positions. Extremely large, air-launched versions are designed to destroy caves and tunnel complexes.