Seize Them All! (Updated Dec. 11. 2021.)
This mod lifts the limit on the number of generals you can take as prisoners of war when you win a battle.
Up to 4 legions can participate in one battle, so you can take up to 12 enemy generals as prisoners.
Of course, since AI is also applied, your generals may be captured and executed in large numbers, so please be careful when using them.
And without enough reserve generals to replace the executed generals, the game may not progress.
This is a bug in vanilla, not a mod issue.