Omsk sits deep in Siberia, well beyond the areas Russia had prioritized for protection against Ukrainian drone attacks. The Wall Street Journal reported there was little air defense around the refinery because Russian authorities had assumed it was too far from Ukraine to be at risk. The attack also hit as Russia was already grappling with fuel shortages, long lines at gas stations and rationing.

The deeper Ukraine can strike, the more territory Russia has to protect. That creates an increasingly difficult air-defense challenge. Russia must defend the front line, occupied territory, major cities, military sites and energy infrastructure across the world’s largest country. Ukraine is also intensifying strikes closer to the front lines. In occupied Crimea and southern Ukraine, guided drones have targeted fuel tankers, storage sites, military logistics and electricity infrastructure.