There is a passage in the book, “Charlie Wilson’s War” about a Special Forces captain who worked with the CIA to arm the muj in Afghanistan. He scoffed at Charlie Wilson’s desire to get the muj the Oerlikon cannons to kill the HIND gunships, and said that it would be “the right mix of capabilities” that included short range anti-air missiles like Stingers and Blowpipes, but also heavy machine guns, and appropriate ground arms.
Right now the US Army has but one tank, the M1A2 Abrams, which is on the “Systems Enhancement Package version 3” which is essentially all the electronics and some of the “TUSK” (Tank Urban Survivability Kit) capabilities. And the US Army has a lot of them, and Congress continually forces the Army to buy more of them.
The Abrams is heavy, not very efficient on fuel, and has a crew of four. It is a good tank, although it isn’t strategically mobile, nor tactically mobile. It requires a tractor trailer to move it around before dismounting to fight. It’s a maintenance queen.
The Soviets encountered many of the same downsides with the T-64. It was high tech, a bit heavier than normal for Soviet tanks, which trend lighter than their American counterparts. The Soviet answer was to create the T-72, which was simpler, cheaper, and more reliable. Premier units got the T-64, and the bulk of the Red Army got the T-72.
But the Soviets did not stop making the T-64, and continued it’s upgrade path with the T-80 and T-84. The T-72 also got the upgrade path with the T-90 and T-73B3. Eventually the T-72B3 became the standard as the advantages of the “higher tech” T-64/T-80/T-84 tanks just became too expensive for the supposed advantages.
Of course talking about just the tanks isn’t really talking about the “right mix” of each nation. The US Army has the Bradley Fighting Vehicle. Which is a good fighting vehicle in terms of firepower, horsepower to weight, and efficiency. The Russians have a whole shmuck of different tracked and amphibious fighting vehicles, some of which are also tank killers in their own right.
Right now the biggest drive for tanks is not bigger cannons or “tank guns” or stronger armor, it’s active protection systems, communications, and better all conditions optics. In short, all of the cool advantages of the M1A2SEPV3 are getting applied to T-72B3s. Individually the Abrams is still the better tank, however as part of a combined arms team, the T-72B3s are definitely part of the “right mix” of capabilities. The new T-14 Armata family of tanks and fighting vehicles doesn’t offer any new capabilities on the battlefield in terms of range or firepower, although it does have one less crew member.
So the trend really is clear, there isn’t much to be gained by going to a new tank platform at this point. Although the Germans are working on a new tank with the French that’s really because they were stupid about their drawdown and scrapped so many Leopard 2A4s that they now only have a limited number of Leopard 2A6s. Ironically Poland has more Leopard 2 tanks in service than Germany.
The current trend is add reactive armor and an active protection system. If the US builds a new tank at this point, it should be in the 35 to 45 tonne range, built for ease of maintenance and crew survival. After all, the upgrade path for everything else is going to naturally occur the way it did for the Abrams, T-64, T-72, and Leopard 2s.