Well, I've been DM-ing for 30+ years, and DM-ed B2 more than once, way back in 1982 (-ish) with D&D Basic rules.
I've been thinking back to how did this then. Movement was simpler, but there was the same lack of rules for defending your allies.
Mostly we played "theatre of the mind" style, and if combats got complicated we'd scribble a diagram (not a battleboard, just an explanation from the DM so the players could make sensible decisions).
About 90% of the time, combats worked in one of two ways
1) Locked down in a corridor or choke point, with one or two melee PCs at the front, and ranged attacks/spell support from the back. The fact that no-one could move through each others space, and there were no rules for pushing past or controlling enemies made this a solid, simple defence. The most vulnerable thing was fear effects or save-or-dies that broke the front line - however these were usually associated with solo monsters
2) Open melee, anything could attack anything. Always bad for the smallest group. Fun when there was a solo monster and the thief finally got to run around the back and use their backstab (this got used way less in basic editions as I recall, the thief wasn't really a major combat character).
In general, as the active explorers, the players got to try and instigate the setup that suited them best. So they would get into the entrance, form a phalanx and bash their way through as many bad guys as they could handle moving down a corridor, and holding doorways as choke points. If outnumbered in a room, they'd back up into a corner to get defence against numbers. If they outnumbered a monster, they'd pile in, and try to ensure everyone got an attack.
It was very static. The only time differences in speed/movement came into play was in chase scenes. Occasionally the thief would climb up and over to attack the back at a key moment. Sometimes there would be a way for monsters to move around and attack the rear of the party.
In terms of years playing different styles, I have probably played this style more than any other. I have to say it works, it's probably much more realistic than the dynamic always-moving battles that 4e encourages. But after a while I did find it a bit simplistic and boring. Moving to the battleboard felt "right" to me. So I'm looking forward to seeing what the grid play extensions to the core will do for this.