Baery's Roaring Death Legion, Shield of Light Legion, and Blackania City's city guards combined with Kumaraghosha's Shansa army, the Church's Knights, and the druids, had made a very large and impressive army camp outside of Diamond City. Baery only blocked off three of the city's gates, leaving the eastern gate wide open. This way, if Edward the Eighth leaves through the eastern gate, it would be easy for the army to attack him.
Not only was Edward the Eighth's army severely outnumbered, the sheer amount of top level powers gathered outside the city was enough to make anyone pale in shock and fear. Despite having the upper hand, Baery did not attack the city immediately. Yolanthe wanted occupation, not destruction. In order to take over the city, the most important part of the plan was not outside the city, but within.