Pacifist by necessity not by creed. They weren't in power and were being persecuted by Jews and Pagans. Also why would Christians want to fight for states that were literally feeding them to the lions?

They had no other choice. (A cynic, though not me, might argue that martyrdom was also better propaganda to use to reach converts at the time than open rebellion but that's another topic.)

Rome didn't become a pacifist state when Constantine converted, did it? I can't think of one and I don't think there is a time when Christianity has been the established and dominant faith in a realm where that realm suddenly became pacifist. If you know of one feel free to correct me.

Edit: It's funny because the more I think about it the more I realize just how similar the position of early Christians and White Nationalists today are. A beleaguered and often persecuted group. Small in size but intense in zeal. Both having truth on their side and both thinking to a day when the world would know we were right. Back then like today it would be insane to try to use violence to win the victory they needed. Back then like today violence destroys everything good we work for and sends us back a decade whereas martyrdom -- not even by death but just by unjust persecution by our enemies -- makes us sympathetic to many and advances our aims. Also how many times have you heard WN's quite rightly tell other young men to absolutely under no circumstance join the army? You're just a soldier for Zion if you do that but you're not a pacifist when you say that and that's the way I'm sure the early Christians felt about being soldiers. Why would I fight in the name of Satan's power on Earth that persecutes me?

But we're not pacifists any more than the early Christians were.