Territories : Deluge and APIs

Territories : Deluge and APIs

I am trying to work out how to filter a deluge query by territory eg
  1. "SELECT Total_Amount, Stage, Closing_Date, Created_Time, Deal_Name FROM Deals WHERE Stage in (" + varBaseCriteria + ") AND Territory = 'Territory1'"
The problem being that Territory isn't saved against the Deals table.

After looking through the API documents : https://www.zoho.com/crm/developer/docs/api/v8/territories.html
I can't seem to find anything that will give me a list of what deals are in what Territory.

I've thought about using a workflow to add the Territory to a text field on the Deals record, but don't seem to be able to access any of the Territory fields that way - then I run in to the same issue which is not being able to return a list of what Deals are in what Territories.

What am I missing ?
Why can't I report on this with Deluge ?