This appears to be a fresh season for testing advanced missiles. China tested a nuclear-capable hypersonic missile that circled the globe before heading towards its target - a demonstration that Beijing's capabilities in such weaponry are far more advanced than previously thought. In its wake, North Korea, China's only treaty ally, conducted a test of a submarine-launched ballistic missile into the waters off Japan. Both developments are destabilising: While hypersonic missiles fly at about five times the speed of sound but are slower than ballistic missiles, their menace comes from being more manoeuvrable in flight and hence difficult to track and destroy. North Korea's test was the second time it had launched a ballistic missile from an underwater platform.

While officials in Washington, Seoul and Tokyo as well as analysts worldwide mull over the implications of these tests, it is important to note that hypersonic missiles are already in service in the Russian armed forces, and the United States, too, is developing similar weapons. The existence of a Chinese hypersonic weapon has been known since Beijing displayed one at its National Day military parade two years ago.