User blog comment:DrMabubuse/Camelots army/@comment-4384546-20111230055348

Morgana wants Camelot for a few reasons - She believes its her by birth right, since she is Uther's daughter - She wants to spite Arthur and Camelot is the most important thing to him - Her arrogance as she probably wants to prove she can beat Emrys

Camelot is the largest land in all Albion, it covers the most area and it has very healthy soil for food growing (which is why very few people in Camelot are actually very poor. Look at Gwen's house and how most people in Camelot are relatively well dressed and fed despite being peasants).

Camelots army is actually quite large but all those times its been invaded it has needed to be sneaky, a full frontal assault on the city would be suicide. For example Morgana and Mourgause needed an immortal army and an army of the dead to beat their way into Camelot. Then in season 4 they needed to sneak in through the tunnels in order to get close enough to be a threat.