New Delhi, Aug. 16 -- For six months, British-built drones have been crossing into Russian airspace and striking oil refineries hundreds of miles from the front line. The program has remained largely unacknowledged in London, publicly undefined in Kyiv, and quietly consequential in ways that are now difficult to contain.

oil refineries near Moscow, Yaroslavl, and Volgograd, along with facilities in Belgorod, the Russian city roughly twenty miles from the Ukrainian border.

"Most deep-strike missions are conducted using Ukrainian drones," a senior Ukrainian military official told The Times, speaking on condition of anonymity because they were not authorized to discuss the program, "but the Armed Forces have also had significant success wi...