Russia has over 3X the manpower of Ukraine. And originally had 4X Ukraines’ regular military establishment.
And so after six months Russia suffered enough casualties to its regulars and conscripts that its had to go to two rounds of mobilization of reservists. And moreover has plumbed all options in unconventional recruitment.
Its telling then that after a year Russia is even starting to feel a strain on its unmobilized manpower reserve.
Wagner had also lost 30,000 prisoners over the past 2 months trying to take Soledar and Bakhmut. No more prisoners are available for cannon fodder so Putin is preparing to mobilize Moscow and St Petersburg residents who have been exempt up to now.