Ukraine’s 3rd Army Corps took the lessons of the failed 2023 counteroffensive into Operation Vivaldi. It fought small, and won.

Five months after launching Operation Vivaldi, a local counteroffensive in northern Donetsk Oblast, the Ukrainian 3rd Army Corps has eliminated the Russian bridgehead on its most important long-term objective: the Zherebets River, which flows south through eastern Ukraine and forms a natural defensive barrier east of the last big free cities in Donetsk: Sloviansk and Kramatorsk.

Attacking methodically under strict secrecy, the 3rd Army Corps has pushed back the Russian 20th and 25th Combined Arms Armies and returned 176 sq km of northern Donetsk to Ukrainian control as of 30 September, according to Ukraine's presidential office. The figure could not be independently verified. Operation Vivaldi netted the Ukrainians hundreds of Russian prisoners and erased 18 months of Russian advances toward Sloviansk.

"Ukrainian forces have defeated the 2026 Russian campaign to seize Donetsk Oblast," the Institute for the Study of War in Washington concluded.

It's a remarkable feat for the overall outgunned and outmanned Ukrainian forces. Equally remarkably, the Ukrainians deftly dodged several potentially fatal traps as they flanked the 20th and 25th CAAs. They didn't get stuck in the Russians' dense minefields. They didn't expose themselves to devastating air attack. Perhaps most importantly, they didn't set their sights on distant objectives. They thought small instead of big, stacking small gains on top of small gains until those wins amounted to a big victory.

A trio of US Army officers—Col. Timothy Price, Capt. Patrick Visser, and Capt. Andrew Carter—described this achievement in academic terms. The corps' defeat of the Russian bridgehead on the Zherebets "had little to do with maneuver warfare," the officers wrote for the Modern War Institute at the US Military Academy in West Point, New York.

In military parlance, "maneuver" generally involves heavy ground forces supported by air strikes and artillery decisively breaking through enemy lines and then rushing vehicles and troops into the panicking enemy's unguarded rear area to quickly inflict maximal destruction and achieve maximal territorial gains.

That's not what the 3rd Army Corps did in its five-month—and ongoing—counteroffensive. No, the Ukrainians "won through systematic, geometric interdiction and positional pressure," Price, Visser, and Carter wrote. Put plainly, the corps carefully probed for tree-covered assault lanes toward key settlements, deployed unmanned ground vehicles to clear mines and explode the most important nearby Russian strongpoints, and then rushed in armored vehicles carrying infantry.

They marched step by step, incrementally liberating a kilometer at a time instead of running a marathon toward a major objective tens of kilometers away. In that way, Operation Vivaldi is the very opposite of Ukraine's failed 2023 summer counteroffensive, which massed tanks for what commanders hoped would be a decisive breakthrough around the village of Mala Tokmachka in southern Ukraine's Zaporizhzhia Oblast.

The objective at that time was to break into the Russian rear and speed tanks 80 km to the occupied city of Melitopol near the Sea of Azov. That never happened. The Ukrainians got mired in minefields around Mala Tokmachka, suffered badly from Russian air attacks, and, after a grueling season of costly attacks, lost momentum just 10 km south of Mala Tokmachka. Later Russian counterattacks erased even those modest Ukrainian gains.

Old thinking versus new

The planners of the failed 2023 counteroffensive were stuck in an old way of thinking about maneuver warfare. The planners of the successful 2026 counteroffensive shrugged off obsolete ideas. They thought smaller—and, ironically, achieved much more as a result.

The 3rd Army Corps couldn't, and didn't, do it alone. Indeed, the corps depended on the Ukrainian Unmanned Systems Forces to fray the Russians' supply lines, electronic warfare teams to jam Russian drones, and the Ukrainian air force to bomb Russian drone operators the EW teams couldn't suppress. By contrast, the Ukrainian forces attacking south from Mala Tokmachka in 2023 did so without much aerial support.

The aerial and electronic preparation was a prerequisite for each of the 3rd Army Corps' incremental advances this spring and summer. The lesson, the officers argue, is that "higher headquarters must degrade key enemy capabilities" before a smaller ground formation can expect to gain ground and keep it. If the support falters, the ground forces won't be able to hold.

Think small. Prepare hard. Now that the Ukrainians know this is how to win on the ground, can they repeat Operation Vivaldi's success?

There's some evidence they're already doing so in the southeast, where a clutch of Ukrainian air assault brigades has been pushing back the Russian 29th Combined Arms Army.