Fight back during tribute periods: Receiving tribute no longer prevents you from launching a campaign. When a country attacks you, the war cooldown against that country is cleared. Other campaign requirements still apply.
No lengthy cooldown for missed proposals: Campaign proposals that never lead to war no longer trigger the full war cooldown.
Weaker tributary countries act more cautiously: Countries paying tribute now assess their strength against yours more strictly before launching new attacks, reducing reckless aggression after defeat.