War in the air is becoming increasingly significant as conflict on the ground becomes bogged down

First came the sound of drones. Then a boom that rattled windows. Shortly after that, two columns of black smoke rose over the Shebelinka gas processing plant in Ukraine’s Kharkiv region. Towering flames threatened storage tanks.

A refinery worker emerged from the site. Russian drones and missiles had struck the plant at 4.30am, he said. For now there was nothing for the fire crews to do but to stand back and watch.