Starlink helped Ukraine win Operation Vivaldi. A new cap on it could help Russia claw back the ground

The Ukrainian 3rd Army Corps' Operation Vivaldi—its secretive counteroffensive east of Sloviansk in northern Donetsk Oblast—started earlier than first reported, and by the time it ended on 14 October it had cost the Russians more than 8,000 troops, by the 3rd Army Corps' count.

It was a major Ukrainian victory in one of the most important sectors of Russia's 56-month wider war on Ukraine. But it could prove to be a temporary win, one the Russians may be able to partially reverse, if the administration of US President Donald Trump continues to throttle Starshield, the military version of Starlink that Ukraine's drones and commanders rely on.

The Ukrainians' former command and control advantage, largely attributable to once-reliable Starlink and Starshield access, was pivotal as Operation Vivaldi played out in the Donbas region in stages starting in March. That advantage shrank practically overnight on 14 October, when a new speed cap began cutting off Ukraine's Starshield terminals whenever they moved faster than about 160 km/h (100 mph).

The 3rd Army Corps attacked east of Sloviansk and north of Lyman as early as March, analyst and mapper Clément Molin concluded after scrutinizing official videos and interviews the Ukrainian defense ministry recently released. "The operation began much earlier than initially thought," Molin wrote.

We are now 5 months after the start of Ukraine's Vivaldi operation and it has now officially ended

A month after the operation was revealed, we know have much more information on the biggest Ukrainian success of the year.

THREAD1/18 pic.twitter.com/MgCoSv7Yhr

— Clément Molin (@clement_molin) October 20, 2026

The timing was probably no accident.

In early February, SpaceX, working from a Ukrainian defense ministry whitelist, switched off the thousands of stolen and smuggled Starlink terminals the Russians had been using.

That had the effect of grounding many Russian drones and blinding many Russian commanders. Taking advantage of the Russians' confusion, Ukrainian troops attacked in several key sectors: in Zaporizhzhia and Dnipropetrovsk Oblasts in the southeast, and east of Sloviansk in northern Donetsk.

The Donetsk attack expanded into a full-blown counteroffensive under conditions of strict secrecy as the 3rd Army Corps probed for weaknesses along the flanks of the Russian 20th and 25th Combined Arms Armies, then overextended along the axis between the Zherebets River in the east and the outskirts of the Sloviansk-Kramatorsk urban conglomeration in the west.

The Russians had been threatening to lay siege to Sloviansk and Kramatorsk, the last two big free cities in Donetsk Oblast, from two directions: the north and the south. Operation Vivaldi eliminated the northern threat—and at great cost to the Russian 20th and 25th CAAs.

Drones lead

Aerial drones and unmanned ground vehicles led the attack, taking the Russians by surprise. "For an offensive operation, the Ukrainians sustained relatively few casualties compared to previous engagements," Molin explained. "Conversely, the defending Russian forces suffered significantly higher losses, largely due to the rapid encirclement of at least three regiments, not all of which managed to escape the area."

It's unclear how many casualties the Russians suffered, but they might number in the thousands. The 20th and 25th CAAs were particularly fragile because the 3rd Army Corps and supporting drone units had been bombarding their supply line with so-called "middle strike" drones.

But many middle strike drones rely on civilian-style Starlink satellite terminals or the more rugged, better-performing Starshield. Now that the 3rd Army Corps has wrecked Russia's 144th Motor Rifle Division, which the Institute for the Study of War assessed on 20 October has effectively ceased to exist as an organized fighting force, and pushed the Russian survivors back to the far bank of the Zherebets River, the Ukrainians are probably "consolidating their gains and adopting a defensive posture," according to Molin.

But that defensive posture, protecting Sloviansk from a northern attack, depends on reliable communications and responsive drones. On 14 October, a new speed cap hit Ukraine's Starshield terminals, cutting the link on any drone flying faster than about 160 km/h. Who ordered it is disputed. Sources told Reuters the order came from inside the White House, and that Pentagon leaders were told the service needed to be slowed.

The Wall Street Journal reported that Musk himself ordered the slowdown, and that he and Trump discussed it soon after it became public. While Trump has denied ordering the speed limit, it's worth noting that the American president has become more overtly friendly toward Russia as his Republican Party looks likely to lose control of the US Congress in the November mid-term elections.

The speed limit renders many of the faster middle-strike drones unflyable. As a result, "Ukrainian drone strikes have diminished significantly following yesterday's crippling of Ukraine's Starlink/Starshield connections, Russian sources report," the military history account ChrisO_wiki wrote on X on 15 October, the day after the speed limit took Ukrainian operators by surprise.

A reduction in middle strikes on Russian supply lines could help Russian field armies recover from recent setbacks, including their retreat back across the Zherebets River. And if the communications confusion resulting from the partial loss of Starlink/Starshield connectivity persists, it could give the Russians the same kind of opportunity the Ukrainians had back in the spring.

An opportunity to go back on the attack—and an Azov communications engineer warned Euromaidan Press in February that the shoe might be on the other foot.

That's the worst-case scenario for the Ukrainians now that Operation Vivaldi has ended. The best case is that they get full Starlink and Starshield access back—or find command and control alternatives—and duplicate, in other sectors, the same success they enjoyed in northern Donetsk.

"Now that the northern flank of Donbas is secured, at least for some time, the focus will concentrate on the southern flank," Molin predicted.