Hypersonic Missiles: Comeback of a Failed Concept?

Hypersonic missiles (HCM) and Hypersonic Glide Vehicles (HGV) are not new but have received a lot of attention as of late. With Russia (Avangard, Tsirkon, Kinzhal), China (DF-ZF) and the US (ARRW, GPI etc) developing and producing new hypersonics and countermeasures, let’s break this topic open and talk about the basics: What are hypersonic missiles, are they scary, what are the countermeasures and what about stealth?

Image: DOD