Growing concern in the US of North Korean troops deployed in Russian territory

The video discusses the confirmation by U.S. officials that North Korea has sent troops to Russia, a development deemed serious by Defense Secretary Lloyd Austin. Satellite images show North Korean soldiers in Russia's Far East, and Ukraine's military intelligence suggests they may soon be deployed to the battlefield. Russia faces challenges in maintaining troop numbers due to high casualties and has resorted to recruiting prisoners and offering financial incentives. The use of North Korean troops is seen as a strategy to bolster numbers, despite the high casualty rates among Russian forces.

What reasons are given for Russia's need for North Korean troops in the conflict with Ukraine?

What does the term 'cannon fodder' imply in the context of North Korean troops being used by Russia?