Ultra-Heavy tanks are a fun concept. Simply scale up a tank to weigh 1000+ tonnes, add a stupid amount of guns and armour, and you end up with something like the image below.
Of course, this monster was never built and if it had, it would have been worse than useless. Ultra heavy tanks would:
- Require as many resources to build as an entire detachment of conventional tanks.
- Be spectacularly slow and unwieldy.
- not be mobile and splittable, like a conventional armoured division.
- be a sitting duck for artillery barrages and aerial bombardment.
- struggle with a number of different types of terrain that more conventional vehicles could deal with.
- require specialised training and manpower requirements to support and operate.
- absolutely guzzle fuel, likely requiring either a non-conventional powerplant or be a logistical nightmare to keep supplied.
- if destroyed in battle, represent an immense and unrecoverable loss of manpower and material.
In the real world, there isn't a single thing that a Ultra Heavy Tank can do that can't be done better by the same cost of conventional armoured vehicles.
But we aren't interested in the real world.
What combination of circumstances would lead to Ultra Heavy Tanks being a sensible and efficient weapon of war?
You are free to tinker with:
- The overall design of the tank, although it should still fit the bill of being a 1000+ ton monster, bristling with multiple oversized weapons systems.
- The technology level of the conflict. I would prefer technology kept to approximately modern day or earlier. No anti-gravity or micro-fusion reactors unless you absolutely have to.
- The foe. Fascist nations, aliens, robots, all are fair game.
- The theatre of war. You are free to posit a war anywhere on or off Earth.
I'm looking for answers that stick with as realistic an interpretation of physics and engineering as possible. Solutions drawing upon Fantasy/magical themes are not in the spirit of this question.