More than 20% of their troops, including their 'elite' VDV (Airborne troops), the Marines, and so called Guard tank brigades you call 'a small portion'?
The 900K active duty number is across all services. The active duty Army- the part that is used in Ukraine, was 280K. That's everyone, including non-combatants, and half of those are conscripts. Combat forces are much lower, which is why the proxy militias and Rosgvardia and Wagner mercs are the actual ground combatants.
The aerospace forces and navy are not really a factor as far as this war goes. The VKS never established air dominance and the Ukrainian airspace has been contested from the outset. And they don't have all that many tactical aircraft anyway, and they've lost several high-end airframes including the SU-35S with the latest EW pod.
The Black Sea Fleet can shoot Kalibr missiles from a distance, but it is a fixed asset in terms of numbers. It won't get larger, or play a larger role. The phibs can't get to Odesa because Harpoon and Neptune guard the path.
Ground forces are all that matter here.
Russia committed about 70% of it's active combat units to Ukraine in the invasion. (120 of 168 BTG's).
The ad-hoc battalions that have been formed since April appear to be run at about 50%, so a tank company that would have had 10 tanks only has 5.
Russia has been trying to increase their manpower in various ways, with mixed success, and this years conscripts will not meet the target of 143K. There are several reports of the Russian army and Wagner recruiting experienced troops from prisons.
The Russian success in the Donbas is because they are burning through old soviet stocks of ammunition at a mind-dumbing rate. 45,000 shells in one day on the Izium axis a while back- 360 artillery pieces, 125 rounds per day per.
SDonetsk averaged 20K rounds a day. They just shell until the UA leaves, then creep forward through the rubble until they make contact again. The scouts from the LDPR have that job (which doesn't have much of a future).
They can't burn through ammunition like that and sustain it. That's why we saw the ammunition trains Belarus and Crimea the last couple weeks. That's even older soviet-era stock than what they've been using- not particularly stable and not particularly reliable. e.g 40% dud rates, and not every ammunition dump that goes up is necessarily from HIMARS, if you know what I mean. Some of those explosions are "naturally occurring".
The Ukrainian campaign against the artillery infrastructure is working. They are reaching all the way to the railheads where the main warehouses are. Kill the trucks, break the logistics, you take the artillery out of the fight.
