A Russian officer surrendered and sold out his comrades, helping Ukraine's special forces cross a key river

• A Russian officer helped Ukrainian special forces secure a key river, the AP reports.
• The officer and a group of 11 other soldiers surrendered along the Dnipro river.
• The intel they gave helped Ukraine establish a bridgehead on an island, according to the AP.

A Russian officer who opposed the invasion of Ukraine surrendered on the frontlines — and provided intel that helped Ukrainian special forces secure part of a key river, according to the Associated Press.

Amphibious troops with Ukraine's elite Center 73 special forces had been trying for months to take Russian positions along the Dnipro river, the AP reported.

But after Russian forces blew up a dam upstream and flooded villages and towns in June, Ukrainian forces were forced to pull back. By the time the waters receded in July, Russian troops were able to retake their side of the river, according to the AP.

One unit of Center 73 was tasked with retaking an island near the village of Krynky, the AP reported, but the Kremlin's forces drove them off under a hail of gunfire and Iskander missiles.

Not long after, a Russian officer who opposed the war was transferred to the frontlines, according to the AP. The officer approached Ukrainian intelligence and offered to surrender along with a group of 11 other soldiers who were also disillusioned with Russian President Vladimir Putin's invasion, the outlet reported.

The Russian troops surrendered to Ukrainian special forces and fed them information about the remaining Russian forces, according to the AP.

That helped special forces stage a breach in the Russian position and establish control of an occupied village across the river, according to the AP. Ukraine still holds the area.

Still, the foothold is just a small breakthrough in the larger war that has become a grinding, bloody stalemate between Ukrainian defenders and Russia's invasion forces. Beyond the bridgeheads, the Dnipro river remains a formidable natural barrier between Ukraine and Russian-occupied territory on the river's left bank.