Technically, there was no Babylon 1. When you only expect to build one of something, you don't number it. The first station was called The Babylon Station. It was destroyed, along with the next two, by home-grown Earth terrorists groups (apparently not the same one each time) who were oppposed to the entire concept of The Babylon Project. All were destroyed fairly early in the construction process and therefore each subsequent station could be built with parts and modules left over or salvaged from the previous station.
Up to Babylon 4, that is. That was complete and on-line when it vanished, all six-miles of it, including the engines, heavier armament and other things that Babylon 5 wouldn't get.
When B4 disappeared Earth came very close to abandoning the Babylon Project. For one thing, they were still recovering from the E-M War and pouring a lot of money into rebuilding the military. The Babylon Project might have been designed to prevent another war, but EarthGov was hedging its bets by making sure at the same time that we would be better equipped to
fight another war if it came to that. Earth simply could not
afford to build another giant space station way the hell out in the middle of nowhere again.
That's when the Minbari stepped up to the plate and offered to help finance a new station - in exchange for certain "considerations" The Centauri also chipped in, reluctantly. Thus Earth was able to scrape together a scaled-down version of the original Babylon Station. The place was still under construction during the series, which is why the industrial areas like Gray sector could have lots of unfinished space, and why someone could make an entire level of it disappear without anyone knowing it.
Regards,
Joe
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Joseph DeMartino
Sigh Corps
Pat Tallman Division
joseph-demartino@att.net