As writers with more military experience than myself have noted, the Russian approach to making new tanks is evolutionary rather than revolutionary. The T-90 is an updated version of the T-72, which is an updated version of the T-64 etc. Engines may get better and have more power. Optical sighting may improve, but the basic design remains the same. One huge problem with all Russian tanks is the storage of ammunition around the inside of the turret. Thus the rather spectacular videos we have seen of Russian tanks looking like jack-in-the-boxes as their turrets are blown hundreds of feet into the air when struck by an anti-tank guided missile setting off stored ammunition. That was a design flaw that I suspect was not anticipated by any of the participants. Since the T-90 is just as vulnerable to this as a T-64, it strikes me that the primary reason to use T-64s is that the Russians may be running out of their T-90s. I don’t really think they are keeping them in reserve.
By some estimates since the beginning of the invasion in February 2022, Russia has lost at least 4358 relatively modern tanks (out of about 6000). Others put the number lower at about 2000 (out of 3400). The discrepancy seems to be due to the difference between the total number of “operational” tanks possessed by Russia pre war, versus the number which was committed to combat at the onset of the invasion. In either event, the losses represent about 2/3 of the pre-war inventory. Russia on paper also had 8 to 10,000 tanks in storage. However, many were poorly maintained and are not in running order. To show how depleted the Russian inventory is, older T-54s and T-55s from the Korean War era and even T-34s from WW2 have been seen in combat in Ukraine. Some have been taken from museums and refurbished. It appears that what we are currently seeing on the battlefield represents the dregs of the Russian inventory that it can muster to put into combat.
The lack of T-90s on the battlefield at this time seems to be more indicative of a depleted inventory than a tactical decision by Russia to withhold it’s best battle tanks from the war.
