All-robot assault opens new chapter in front-line warfare

In a snowy forest not long after dawn, a four-wheeled drone churned through the mud toward its target: a Russian bunker, where it eventually arrived and exploded.

- Alistair Macdonald & levgeniia Sivorka

More drones followed. Some moved on land, including ones mounted with machine guns or packed with explosives. Others came by air, dropping munitions and providing a view of the battlefield.

The attack by the Ukrainians in December coordinated unmanned land and aerial vehicles on a scale that hadn't previously been done, marking a new chapter of warfare where humans are largely removed from the front line of the battlefield, at least in the opening stages.

The Ukraine war has led to a rapid evolution in drone warfare, as both sides have continually innovated in an effort to get an upper hand. Though it was later rescinded, the recent halt to U.S. military aid and intelligence sharing only highlighted how vital drones are to Ukraine as it tries to hold out against the Russians, who have a manpower advantage of 5-to-1 on some parts of the front line.

The December attack involved about 50 unmanned aerial vehicles and destroyed a Russian position north of the eastern Ukrainian city of Kharkiv, according to the force that conducted the operation, Ukraine's 13th National Guard Brigade.

The Wall Street Journal viewed video footage of the assault.

The attack served as a proof of concept. Though it had its problems, other Ukrainian units are now planning similar missions.

It did have some teething issues. The land drones in particular struggled with the terrain. And, while the drones did the fighting, good leadership, planning and drone operators remained essential, the U.S.-trained brigade said.

When the five-hour operation ended, Lt. Andriy Kopach, who specializes in land drones, was so exhausted he could think of nothing but sleep.

Later, as international companies and governments began to reach out with questions about the attack, its significance became clearer.