[kodyo]

The empire has vassals, not allies.

[amarcheschi]

The empire is doing everything it can to alienate its vassals into indipendent cities-states with their own alliances

[dmitrygr]

Vassals who refuse to bend the knee tend to ... not live long. Often replaced by those who bend it properly.

[estearum]

Realpolitik dictates that you don't start conflicts with all of your vassals for literally no reason

Satisfied?

[FpUser]

You nailed it

[markus_zhang]

Good point but not popular here.

[Starman_Jones]

It's old thinking that has been proven wrong multiple times... by America.