What army do I need to attack a Wilderness in Dragons of Atlantis?

I decided to be sensible and scout a level 9 Wilderness before attacking it and found out it had at least 5000 Stenches:

What size of army from my side would I need to defeat them and how can I estimate what army I'll be up against in the future?

Any suggestions on upgrades and unit composition would be welcome!

Anthropus and Anthropus Camps may answer your questions.

Those two pages define unit composition and what the stats of each unit are. You can easily calculate using those two pages the over defense, attack, and life of the units you will be up against.

In their question asking how can I estimate what army I'll be up against in the future is answered completely by the table on the Anthropus Camps page linked to above. The Anthropus page tells you for example that 5,000 Stench have a combined 25,000 attack, 25,000 defense, 50,000 life, and a speed of 3000.