Hypersonic weapons were recently in the media spotlight when Russia claimed that the Ch-47M2 Kinzhal missiles used in its war of aggression against Ukraine were a new type of hypersonic weapon, the first of its kind in the world, and could not be stopped by any existing defence system. Hypersonic weapons are characterised by high speed (at least 5 times the speed of sound) and the ability to make unpredictable course changes during flight. They can carry both conventional and nuclear warheads. Two types of hypersonic weapons are relevant today: Hypersonic cruise missiles with air-breathing engines and hypersonic glide vehicles without their own propulsion. These are not entirely new technologies: Both types are further developments of existing cruise missiles or intercontinental ballistic missiles. This development has been increasingly promoted by the major powers, the US, Russia and China, and to some extent by other countries since the Anti-Ballistic Missile Treaty was denounced in 2002. From the perspective of strategic stability, hypersonic weapons pose an enormous challenge because the ambiguity of their trajectory and thus of their intended target, as well as the lack of clarity as to whether they carry conventional or nuclear warheads, complicates the determination of the defensive response and increases the risk of unintended escalation.