Big politics in ttprpg

Have you ever tried doing some political machinations or succesion crisis in your games? Game of Thrones kind of thing?

I love these plots and would love to have the neighbouring kingdom rallying an army against my players' one, but I doubt DnD is even the right tool for that. I think it's a system meant for a few characters fighting small groups, not for rallying armies or great battles. Even the swarm rules present in the textbook are more oriented for swarm fighting a small party, not another swarm.

Did any of you ever try something like this? How did you do it? Do you reccomend any other system or perhaps you found a way to implement it into DnD?

What's important here is that I DO NOT look for a way to fight big battles, I look for a way to implement big politics in general