Achievement is Awarded for belonging to a team that holds one or more territories in all areas.
Now the easy way to get this is to play offline (so unplug that cord). every Territory will only cost 3,000 instead of the 50,000 like online. Now if it looks like your going to fail dashboard out show you don`t lose any points and try again, It took me many try`s to succeed. All Territory will have 2 AC`s and 5 Choppers, now some will be easy others very troublesome, depending on your skill these will very. Some I destroyed the AC`s others were just the choppers do to the power of enemy AC`s and my limited skill.
Hope this helps.
P.S. You can not get the Overlord
Achievement (Awarded for belonging to a team that holds ten different territories at the same time.) And Customize Territory
(Awarded for acquiring territory and uploading custom gun battery positions.) this way, it has to be done online.