Erfworld 83, Page 77

[Querzis]

How would they convince Ansom that Stanley isn't in the city anymore? Stanley left while veiled. Ansom has no way of knowing if Stanley is inside the city, veiled with his dragons, or outside the city, veiled with his dragons; but cannot risk leaving such an important, defensible location available to Stanley in any case... and Stanley, for his part, has every incentive to let Ansom think that he's still in the city, since it reduces the chance of pursuit.

(Regarding the fact that he only took a few soldiers: Likely there are limits to the number of units that can be veiled.)

Easy, he let him enter the city, not that complicated. A white flag isnt something Stanley would ever do anyway, they just have to show him that hes really not there anymore as well as the twenty dwagons. They can take their time to negociate, nobody is in a hurry. Ansom woudnt ignore a chance to settle things peacefully.

And I guess you are right about the veiled units.