halacha - Meat at a Seudat Mitzvah

Is there any unambiguous source which says it is a halacha to eat "meat" at a Seudat miztvah?

I am aware of the many opinions which says that meat is only optional. I'm looking for sources which say it is not

Answer

In Tshuvos V'hanhagos 3:294, R. Moshe Shternbuch writes that ideally a bris should have a seudah with meat because of the use of the word 'sasson' (in addition to simcha) which implies a more extravagant affair -- something which people will notice as being fancier, like a wedding seudah. So at least for a bris and wedding seudos mitzvah, it would seem ideal to serve meat.