Yes there were, as Reality Chuck points out. Leone even got the names of the generals right. The battles are generally ignored in most books because they were so inconsequential in the bigger picture. But they were pretty important to the guys fighting them!
I should have said that the vast majority of spaghettis were filmed in Spain - especially in southern Spain, but elsewhere also. And that many interior scenes may have been shot in Cinecitta Studios in Rome.
According to Roger Ebert in the liner noted of the re-release special edition 2004 of GBU liner notes, Eastwoods’ character in FFOD is Joe, FFDM is Manco and GBU is Blondie.
Just got it yesterday and am going to try and watch it before football today. It includes 18 minutes of additional original footage.
Leone made two other masterpieces, Once Upon a Time in the West 1968 and Once upon a Time in America 1984. You have to see the uncut DVD versions.