You have watched the TV movie "Babylon 5: In the Beginning."
"In the Beginning" tells why how the Babylon project started. The war you saw was the Earth/Minbari War.
Babylon 5 is a great show. You NEED to watch the first season. Since the show was written like a book. Because J. Michael Straczynski (Creator and he wrote over 90% of all the episdoes.) made the show into a 5 year story arc and a novel, so the series had a beginning, middle, and a end.
The Seasons:
Season One: "Signs and Portents" Exposition
Season Two: "The Coming of Shadows" Rising Action
Season Three: "Point of No Return" Climax
Season Four: "No Surrender, No Retreat" Falling Action
Season Five: "Wheel of Fire" Denouement
If you want more information:
http://en.wikipedia.org/wiki/Babylon_5