North Korea has reportedly stiffened its perimeter defences along the east coast, deploying ballistic missiles as well as additional ground forces and anti-aircraft batteries.
The shouting match between Washington and Pyongyang has had an increasingly belligerent physical aspect, as B1 bombers flew up the North’s east coast on Saturday.
The 1950-53 Korean War was ended by a truce only, and the country remains technically at war with South Korea and its major backer.
A fresh round of UN sanctions hit the country following its sixth nuclear test this month. It has also fired dozens of missiles this year, some passing over Japan with at least one believed capable of hitting America’s West coast.