For Marche, his complaint is that Enweil refused to break the agreement afterwards once they had their Capital back. That is the slight difference. Marche understood the surrender, but Riombara demanded that Enweil rejoin the fight for Humanity once they had recovered and asked Enweil to join Riombara after they had lost their Capital for the second time, promising them their sovereignty. They refused to do either. That is where the crucial difference lays. Not so much the surrender in the Fifth Invasion, but their refusal to rejoin the fight afterwards is what pissed Marche off at that time.
P.S. I agree that difference is small, but it is a crucial one for my character.
Poll