Quote Originally Posted by Darth Ultron View Post

The shadow warrior was an example of a ''new'' race on the prowl? Ok....

And sure, some characters...mostly G'Kar have thought a ''new '' (or old) race with a advance and powerful military have been ''around'', but we don't see the Earthforce people saying or thinking that. Even in this episode they are like ''um, a mystery'' attacked the Narn place...and not ''It must have been a ''new '' (or old) race with a advance and powerful military.
The humans have been hearing rumors of something out there that's new to them. But it's not hard to believe that they think that anyone with the military presence to wipe out a Narn fleet is something they would have heard about well before now.

Part of this whole arc is them slowly coming to the realization that there's a force out there that is a match for Vorlons that they didn't have a clue about.

It'd be the same if race of mole men that live 100s of miles below the surface eliminated the dinosaurs, and have just been biding time for millions of years. It's not going to be our first thought, because we'd assume anyone that powerful would have been active.