An anonymous U.S. defense official estimates that Russia has lost anywhere from 15 to 20% of its combat ability, reports ABC.

While some Russian troops have retreated from cities in Ukraine, some Russian battalion tactical groups (or BTGs, with roughly 800-1,000 soldiers each), have withdrawn back across the Belarusian and Russian borders and have been essentially "eradicated" from the fighting in Ukraine.

"There's just nothing left of the BTG except a handful of troops and maybe a small number of vehicles," the official stated.

When accounted for, including tanks, troops, aircraft, and missiles, the official estimates Russia has lost between 15 and 20% of its combat power, initially marshaled in its invasion of Ukraine.

The official adds that some of the withdrawn forces are on their way to the Russian cities of Belgorod and Valuyki, to the northwest of Donbas. However, there are "no indications" that new troops are waiting there to join them.

For now, the official continued, remaining Russian BTGs are "exploring the option of" banding together troops and supplies to form new units.

Additionally, Russia is seeking to recruit north of 60,000 new troops.

The official believes that after Russian BTGs consolidate, "the most likely course of action would be for them to move immediately south right into the Donbas." The Pentagon believes roughly 40 Russian BTGs are positioned in or near the Donbas region.

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