A Russian air force Il-76 airlifter was rolling down the runway at Saki air base in Russian-occupied Crimea on Tuesday afternoon when something—or several somethings—exploded hundreds of yards behind it. As many as a dozen blasts rocked the sprawling base, which houses the Russian Black Sea Fleet’s 43rd Independent Naval Attack Aviation Regiment and other units. Fireballs rolled into the sky, feeding a pall of black smoke and startling tourists sunbathing on nearby beaches. The Kremlin claimed the explosions were the result of an accident. But the near-simultaneous blasts across the airfield indicated otherwise. It clearly was a Ukrainian attack. But exactly how the Ukrainians hit this major Russian facility 120 miles from the front line remains unclear. But they had options. In the five months since Russia widened its war in Ukraine, the Ukrainian armed forces have deployed more and better means of conducting deep strikes . Even a hundred miles from the front, the Russians are vulnerable. The Saki base immediately prior to the attack housed around a dozen each Su-24 bombers and Su-30 fighters plus Mi-8 helicopters and the Il-76, according to commercial satellite imagery. At least one of the Su-24s was destroyed in the Tuesday attack along with several support vehicles and possibly one of the base’s munitions dumps, if videos and photos of the damaged base are any indications. It’s possible the damage is much more extensive than the initial evidence implies. The Tuesday raid marks the latest escalation by Ukrainian forces that steadily are growing more adept at pinpointing and hitting Russian bases, supply lines and command posts—sometimes inside Russia itself. It also signals the ongoing degradation of the Black Sea Fleet. In five months of missile and drone strikes, the Ukrainian navy has sunk the fleet’s flaghip, Moskva , in addition to several support ships, amphibious vessels, patrol boats and landing craft. A Ukrainian drone bombed a Black Sea Fleet headquarters in Crimea in the middle of a ceremony marking Russia’s annual Navy Day holiday last month. Even if the Saki base personnel quickly repair the damage and replace any wrecked aircraft, the Tuesday attack was a propaganda victory for Ukraine. “The Ministry of Defense of Ukraine would like to remind everyone that the presence of occupying troops on the territory of Ukrainian Crimea is not compatible with the high tourist season,” the ministry quipped on Twitter . The roster of systems the Ukrainians could have used to strike Saki is testimony to their growing deep-strike capabilities. Options include fighter-bombers, Tochka ballistic missiles, drones and Harpoon and Neptune anti-ship cruise missiles with their secondary land-attack modes. It’s even possible the Ukrainian army managed to complete the new HRIM-2 or Sapsan ballistic missiles it was developing before the war. Fighter-bombers and cruise missiles aren’t hard to miss as they roar overhead—and there’s no evidence of them over Crimea on Tuesday. That could leave ballistic missiles and drones as the likeliest offenders. Ukrainian officials were coy, simply stating that the weapons that struck the Russian base were “exclusively of Ukrainian manufacture. ” That could rule out the American-made Harpoons. Add air bases to the long list of Russian facilities that no longer are safe as the wider war grinds toward its sixth month and the Ukrainians work to shape the battlefield and clear paths for what are, at present, tentative counteroffensives in the east and south. .