it can only be against the dominant power. Anyone at war with them can form itYou have to declare war on one of the two dominant powers, or you must be one of the two dominant powers. Then you may add people to your coalition.
I'm France and attacked Prussia. Then they formed a coalition against me and invited Austria and Great Britain.
Why can't I form my coalition against them now? Where do I see who the other dominant power is?
Could it be Russia?
it can only be against the dominant power. Anyone at war with them can form it
The dominant countries' flags are at the top of the screen. Coalitions can only be formed against a dominant country. In this case, Prussia isn't dominant so you can't form a coalition against them.