[quote=VKAllen]
I think there would be more than just the Titan.
[/quote]

What makes you so sure? You do realize how powerful a Titan is? Don't you? 3 Warhounds (The single weakest of the Titans) managed to decimate the entire of Eurasia during The Battle of Terra. 1 Warlord could do just as much... The Imperium HAD to develop the Volcano Cannon, to mount onto a Baneblade Chassis, JUST so that they had something that could defend against a Titan Attack. Nothing, short of the main cannon of an Emperor-class Battleship (You know the cannon used to commit Exterminatus) will put a scratch against one.

Titans are the Ultimate fighting machines.

That being said, the Titan isn't the only thing that the Word Bearers are here for.