Russian tanks have entered battle for the first time with a new active protection system designed to shoot down incoming drones. But the technology’s recent combat debut in Ukraine met with only limited success—Ukrainian drones still destroyed the Russian armored vehicles by attacking in overwhelming numbers.

The first documented battlefield appearance of the Arena-M active protection system took place when Russian forces launched a company-size assault with tanks and other armored vehicles in the Donetsk Oblast of eastern Ukraine on July 22. The Ukrainian defenders repelled the attack, posting video footage of their kamikaze drone strikes destroying at least seven T-72B3A tanks, including some that carried the Arena-M system.

However, Ukrainian soldiers also described the Russian Arena-M system successfully shooting down some incoming drones. The Ukrainians reported requiring between 15 and 20 drones to finish off each tank. This incident demonstrated that the Russian military is learning and experimenting in how to employ armor on a drone-saturated battlefield.

The development comes more than four years after Russia launched its full-scale invasion of Ukraine in February 2022, as mass armored assaults have become increasingly scarce on the modern battlefield dominated by drone warfare. It’s part of an ongoing arms race where many militaries are struggling to figure out how to protect the weakest points of their expensive main battle tanks and other armored vehicles against swarms of cheap drones.

The Russian military has previously tried adding more physical armor in the form of ‘cope cages’ welded or bolted onto tanks and other vehicles, which inspired the Ukrainian military to do the same. Russian forces even made ‘turtle tanks’ covered in porcupine-style metal spikes and other improvised armor, although the extra weight and encumbrance of such add-ons have often limited both tank mobility and the use of their main guns.