Well, I think that's a bit unfair for land units like tanks and artilleries.
With that, you can finish nearly all battles with aircrafts and paratroopers only.
The tutorial says units with aggreesive orders will automatically attack units of other factions you are at war with.
But I do aggree with this automatic attack should cover an area of serveral pixels along the moving path, perhaps 5 or 10 pixels?