Ukraine’s fight against Russia’s invasion has entered a new phase, pitting home-grown drone technology against a 2,000km (1,200 mile) swathe of largely Soviet-era oil facilities. At least nine major refineries have been successfully attacked this year, currently taking offline 11 per cent of the country’s total capacity by some estimates. As the conflict at the front lines has shifted in Moscow’s favour, the drone campaign is becoming a key plank of Ukraine’s defence – both in its symbolism and its strategic aims.