In the 90s, I spent a lot of time playing air warrior, the first true massive multiplayer platform. The tanks in it were super simplistic. It performed decently over dial up modems and had in game voice comms, multiple mannable gun positions in the same aircraft, etc. At its peak, around 150 people could be in the same world at once. I think the AW crew was involved with several other sims, like warbirds and aces high. Some of them possibly went on to being involved with ww2 online? I bought WW2 online right after it came out. What a disaster it was - it was clear that someone there wanted to to just ship it before it was anywhere near done. I remember it had limits on how many other players you could see in your bubble, so many times you would just die when someone you could not see shot you. They tried to fix the damage as quickly as possible and didn't charge a subscription fee initially, but the launch probably hurt them badly.