Bulgaria gave Ukraine 110 BTR-60 armored personnel carriers. They are 1960s vehicles, too thinly armored to carry infantry anywhere near a front line patrolled by explosive drones. So Ukraine's 3rd Army Corps found another use for them during Operation Vivaldi, its counteroffensive north of Lyman. Fill one with anti-tank mines, rig it for remote control, drive it at a Russian bunker, and set it off.

Packing potentially dozens of TM-62 anti-tank mines, the speedy BTR-60s become what's called vehicle-borne improvised explosive devices, or VBIEDs. Once a favorite weapon of insurgents battling US forces in Iraq and Afghanistan, VBIEDs have found a new niche in Russia's wider war on Ukraine as unmanned demolition systems.

"To break through the enemy's defenses, the 3rd Army Corps employed its own invention, Soviet BTR-60s converted into robotic kamikaze complexes," the corps stated. "They were used to demolish the enemy's strongest fortifications." If an enemy strongpoint is too heavily protected to bomb from the air but exposed to attack from the ground, send in a VBIED.

The Russians were the first to deploy vehicular IEDs in the current war, but the Ukrainians may have mastered the tactic. It's one thing to rig an explosives-filled MT-LB tractor or T-55 tank to roll straight forward without direct human control, as the Russians once did. It's another to rig an explosive BTR-60 to maneuver before going off, as the 3rd Army Corps' VBIEDs clearly did.

On 28 September, announcing the close of Vivaldi's third phase, the 3rd Army Corps released drone footage depicting one of the explosive BTRs blasting a Russian strongpoint north of the town of Lyman. The sheer scale of the explosion is testimony to the VBIED's destructive potential. And the trail the BTR leaves in the grass in the heavily edited video indicates the Ukrainians can steer their VBIEDs around obstacles and guide them to precision strikes.

Why it gets there

A slow wheeled vehicle crossing open ground toward a fortified position should not survive the trip. In most sectors it would not. What makes the tactic work north of Lyman is a condition the 3rd Army Corps built into Vivaldi before its assault groups moved: Ukrainian air defense and electronic warfare threw a protective dome over the battle area, blinding Russian drones so they could not read the operation's design or strike what was moving through it.

Robots have played critical roles in each phase of Vivaldi. Surveillance drones have watched from overhead. One-way attack drones have pummeled Russian positions and supply lines. Heavy bomber drones have not only dropped bombs, they've also airlifted explosive unmanned ground vehicles into position so the UGVs can roll right through the front doors of Russian bunkers.

The self-exploding BTR-60s are too big to airlift, but that's the point. A small UGV might carry a few tens of kilograms of explosives. A remote-controlled BTR-60 can easily haul hundreds of kilograms.

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The arithmetic

It's not impossible to take out a VBIED before it strikes, of course. Mines, anti-tank missiles, and even concentrated gunfire can stop a vehicular bomb in its tracks. But losing one of the aged BTR-60s costs Ukraine very little. The vehicles are too thinly armored for use as front-line infantry transports anyway. You might as well convert them into bombs.

That is the whole case for the tactic. A manned fighter jet lobbing a precision glide bomb is the preferred approach to bunker-busting. But it costs tens of thousands of dollars an hour to keep a jet in the air, and a single glide bomb can cost tens of thousands or even hundreds of thousands of dollars. It's unclear how much it costs to convert a BTR into a VBIED. It could be just a few thousand.

And it reduces Russian fortifications without risking any Ukrainian lives. That's the philosophy underpinning all of the 3rd Army Corps' robot-first tactics. "This is exactly the direction of the corps' development set by Brig. Gen. Andrii Biletskyi," the corps stated, "to reduce the number of fighters in the most dangerous areas and replace them with robots."

Vivaldi began in mid-April under an information blackout that held for five months. The corps says it has regained control of 176 sq km across three of a planned four phases, around half of that de-occupied outright, and taken more than 250 Russian prisoners. Those figures are the corps' own and have not been independently verified.

Sometimes the robots doing that work are 60-year-old APCs modified for an explosive one-way mission.

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Ukraine likely neutralized Russia's drone defenses north of Lyman before sending armor into the third phase of its Vivaldi counteroffensive, the Institute for the Study of War (ISW) assessed. An intermediate-range strike campaign against Russian logistics and electronic warfare paved the way, the think tank said.

Drones have made this front so deadly that armor now mostly fights from kilometers back. That is what makes Ukraine's armored push onto fortified positions near Lyman stand out. Russia has already shifted its effort south toward Sloviansk after losing the Lyman pincer.

Armor reached Russian bunkers without drawing drone strikes

To break the strongest Russian fortifications, Ukraine used old Soviet BTR-60 armored personnel carriers rebuilt as remote-controlled explosive vehicles, the 3rd Army Corps says.

Ukrainian forces drove them up to heavy Russian fortifications without coming under Russian drone strikes, ISW noted. The think tank said this indicates Ukraine neutralized or otherwise negated Russia's drone defenses in the area.

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Strikes on fuel starved Russia's jammers

Ukraine achieved tactical drone overmatch through extensive shaping operations and an intermediate-range strike campaign, ISW said. Those strikes targeted the Russian drones and electronic warfare (EW) systems that would otherwise have hunted the advancing vehicles.

The 3rd Army Corps reported on 17 September that strikes on Russian logistics in occupied Luhansk Oblast had degraded Russian fuel supplies to the front, ISW wrote that day. The corps said that strained Russia's ability to use drones and EW against Ukrainian drones. EW systems consume a lot of power, and Russian troops run them on diesel generators, ISW explained.

Deputy corps commander Maksym Zhorin credited strict information silence and a "Protective Drone" system of EW assets, according to the same assessment. He said it helped neutralize around 20,000 Russian drones. The corps had earlier described mapping Russian command posts and striking them to sow panic.

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Five settlements and 2,000 Russian losses

The corps liberated Nove, Ridkodub, and Katerynivka and restored control over Karpivka and Novomykhailivka, it said on 28 September. The phase added 51 km², bringing the total since the offensive began to 176 km².

Russian losses reached 2,000 personnel, and more than 250 Russians were taken prisoner, according to the corps. Corps commander Andrii Biletskyi said a feint from Shandryholove toward Zelena Dolyna drew Russian reserves away from the real target, Nove.

The first two phases had reportedly cleared more than 125 km² north of Lyman.