>>519273
I know this thread has pretty much hit bottom, but I thought I'd add a brief summary and explanation of the history here.
1) In WWII it became clear that the heavy tanks moving at 5-15km/h on rough ground were essentially so slow that fixed artillery/anti-tank positions could take them out at beyond the heavy tanks range at leisure. Not to mention aircraft, which could not miss the lumbering target. This made the heavy tank obsolete for the one job it was supposed to do - attacking heavily defended fixed enemy positions.
2) So in the end of WWII all the major powers decided that the biggest useful tanks would be the medium tanks, since they could compete with light tanks for speed, and still carry enough armament to destroy fixed enemy positions. And they forgot the reason why they decided that!
3) Improvement in power plants eventually lead to increase in weights of medium tanks until the MBT was developed, which had the weight of WWII heavy tanks yet could move fairly fast on roads. In this way the heavy tank was resurrected, while the medium and light tank designation was ignored, or maintained in small numbers purely for cost reasons in the west, only Soviets maintained medium tanks.
4) In the 60s Soviets made the infantry fighting vehicle to replace the light tank and introduce some utility to it as well, by allowing it to carry a few troops. Other powers copied this and bungled the concept by insisting it only be as mobile as the armored personnel carriers and logistics trucks. The new "light tank" concept then couldn't keep up with the heavy tank, there was nothing in the middle, and the entire armored structure was unbalanced.
5) Nowadays military leaders tend to push for multirole. This is because if every vehicle you have is multirole, you're never left with your pants down by being a bad leader and sending the vehicles for wrong role to do wrong job. In essence it makes officers job easier.
I personally favor resurrection of these old concepts, but revamped to modern battlefields.
>Light tank - Armed and armored against infantry, light vehicles, and light sandbag fortifications. Crew of three to four, can carry three times its operating crew in infantry support (9-12). It's main job is protecting own infantry and engaging enemy infantry positions, armament is focused on that with main gun being a large HMG (14.5-15.5mm) with an AGL or small mortar (50-60mm) for indirect fire and GPMG (7.62) covering other axes.
>Medium tank - Armed and armored against any ground threat that isn't a medium or heavy tank or direct hit from heavy artillery. Crew of three or four, carries twice the crew in passengers (6-8). Main purpose is engaging enemy fortifications, logistics, and vehicles, and acting in insurgencies. Armament is medium caliber high explosive cannon (75-100mm), a heavy machine gun (~12.7mm) and a GPMG (~7.62).
>Heavy tank - Armed and armored against all ground threats, as much as possible. Crew of four to five, usually carries no passengers, but can carry a pair of replacements for crew in long deployments, or an emergency medevac. Main cannon (120-152mm) can penetrate other heavy tanks, several GPMG covering axes for protection. Purpose is destruction of enemy tanks and pushing through heaviest fire to destroy fortification.
All three vehicles fast enough to avoid airborne threats and keep formation, all three vehicles taking advantage of latest in anti rocket protection. Controls inter-operable by similar trained crew, some parts of drive train, tracks, power plant, and fire control system are interchangeable. Entry into a conflict can be scaled; for example if it's a rebellion where enemy just has infantry and civilian vehicles, you send light tanks; if enemy starts using armed vehicles, artillery and fortifications you send in the mediums; and if enemy uses armor or extremely heavy fortifications you send in heavies. Using USA as an example they could get away with having 1000 heavies, 5000 mediums, and 12000 lights and have the better combat ability for same price as 6000 Abrams (underarmed heavy), 6000 Bradley (light with identity complex), 6000 M113 (underarmed light) garbage mix.
But this pipe dream will never happen because if it did, officers would need to be trained to use disparate systems effectively, instead of using multirole system in a mediocre way.