A new technology-sharing agreement enabling Ukraine to manufacture the British-designed Stone Cloak radar jammer domestically is poised to accelerate Ukrainian drone strikes against Russian targets.
Ukraine has already deployed British-built versions of the tablet-sized digital jammer on long-range strike drones this year. However, the agreement authorizes domestic mass production, allowing rapid scaling across Ukraine’s drone fleet.
The British government publicly disclosed Stone Cloak’s existence for the first time on Saturday during Ukrainian President Volodymyr Zelenskyy’s meeting with Prime Minister Keir Starmer at a naval base in Portsmouth. The occasion marked the annual Sea Breeze joint exercise, where Ukrainian, U.S., and British sailors placed “special attention” on countering Russian air defenses, according to Ukraine’s national news agency.
“At this point, we don’t know the full details of Stone Cloak, but suffice it to say, the system will likely increase mission effectiveness against some of the Russian air defenses,” retired U.S. Air Force officer Jeffrey Fischer told Defense One via email.
Ukraine employs a variety of electronic warfare systems in its drone operations, but partner-provided systems like those from the U.K. benefit from larger research budgets and controlled testing environments. These systems can emulate the unique electronic warfare conditions of the Ukrainian battlefield—provided Ukrainian operators participate in development exercises, such as Estonia’s Hedgehog 2025, where a Ukrainian team revealed significant gaps in NATO drone warfare concepts. This makes emerging technology from joint exercises valuable, though the transfer of intellectual property remains rare.
Prime Minister Keir Starmer described Stone Cloak on Monday as “the best of homegrown British innovation, and proven on the frontline” of Russia’s war against Ukraine. That frontline has shifted closer to Moscow, aided in part by British-donated Storm Shadow missiles, which Ukraine has used to strike targets in occupied territory since 2023. However, the U.K. previously supplied only the missiles, not the underlying design technology.
The announcement underscores how rapidly technology sharing between the two nations has evolved in three years, as well as the speed of Ukrainian weapons development compared to some NATO counterparts.
The U.K. spent six years developing and deploying Storm Shadow, relying on specialized European supply chains involving French and Italian partners that complicated technology transfer. The missiles also carried a high price tag, averaging $2 million each.
These factors drove the U.K. and Ukraine into a joint agreement to develop a new long-range strike drone with simplified requirements—a 2024 initiative called Breakstop that British officials say will deliver missiles for frontline use later this year. This timeline—under 24 months from concept to deployment—is significantly faster and cheaper than Storm Shadow. Meanwhile, Ukraine has unveiled its own long-range strike missile, the Flamingo (FP-5), which can also strike Russia at a fraction of the cost.
Fischer noted that the contrast in innovation speed illustrates how such intellectual-sharing partnerships benefit the U.K. as much as Ukraine. “One critical but often overlooked lesson from the Ukraine war is the extremely rapid adaptation cycle Ukraine is able to implement. In some cases, battlefield lessons are implemented in less than 10 days to new systems. In my seven combat deployments, NOTHING has ever come close to that.”
