Did the world just see the first combat use of anti-ship ballistic missiles? Military analysts think so. The weapon used by Iran-backed Huthi rebels to attack ships in the Red Sea was not a conventional sea-skimming variety of anti-ship missiles.

The rebels fired two anti-ship ballistic missiles (ASBM) on Tuesday towards the southern Red Sea, where there were multiple commercial ships, but none have reported any damage.

While one of the missiles splashed into the sea quite a distance away from the ships, another reportedly blew up midair. There is speculation the ASBM may have malfunctioned or intercepted by the US Navy.

To understand why the use of an ASBM is a major escalation, the concept of a ballistic missile needs to be understood first. Ballistic missiles fly a U-shaped trajectory. They are powered initially by a rocket or series of rockets in stages, followed by an unpowered trajectory that arches upwards before descending to reach its intended target.

All long-range strategic ballistic missiles reach outside the atmosphere in its peak and then descend towards the Earth in the unpowered stage. Only the warhead reenters the atmosphere in very high speed of 6-8 km per second, which makes it difficult or nearly impossible to intercept them reliably.

Now, the ASBM launched by the Huthi rebels reportedly appear to be smaller, short-range ones that wouldn’t reach the atmosphere’s edge.