Russia has suffered colossal losses in Ukraine. Is its army depleted?

Russia's military made its largest territorial gains in more than two years in October, as it pressed farther into Ukraine's eastern Donbas region - but at a heavy cost.

British and Ukrainian military officials, as well as BBC researchers, claim that Russia suffered its highest rate of dead and injured soldiers during that month. The arrival of thousands of North Korean troops in Russia is also raising questions about whether the Kremlin has enough soldiers to make up for its losses.

What do we really know about Russia's casualties and its ability to replace them?

The losses that matter

It is difficult to obtain concrete information about Russian casualties, which comprise deaths and injuries. Moscow has an incentive to minimize its losses and rarely discloses any information; Ukraine and its allies have an incentive to overstate them.

Even if...