Ukraine faces a challenging problem: how to stop a resurgent Moscow in its tracks long enough to rotate the troops, resupply, and fortify. Part of the answer is playing out right now in the skies over Russia. Over the past two weeks, at least dozens of Ukrainian drones reportedly struck at least nine Russian regions. The majority of the drones had very specific targets: oil refineries. Many have hit their targets as fires and explosions have been reported at fuel processing plants across Russia. Ukraine has been striking oil infrastructure in Russia since the beginning of the full-scale war bu…