Orks can be dangerous, and we can't have them and the Chaos rampaging through our sectors. I know the Chaos will want to make a large push for Cadia, and as thus will probably throw a fair amount of forces at it. The Ork threat can't be ingnored though. We must make sure that our lines don't break....we can't have an Ork tide come through and weaken the defences to allow an easier Chaos advance. Just my 2 cents.

PS
How many people are going to defend Cadia? It's a prime target and if no one is defending it we could have problems.