Joe and his wife Tiffani are American, and both are born again. Let's just pretend that Canada is (fictionally) an aggressor, throwing Canada's supposed Imperial weight around, and invades the North East Angle, Minnesota. The US, with Joe and maybe his wife, too, in the forces, understandably fights the hypothetical Canadian aggressors. Both Joe and Tiffani have Christian fish tattoos on their wrists.
In the Canadian military, there is a guy called Joe, and he is a born again Christian, too, and his wife Nikki as well. Both Joe and Nikki have similar tattoos to Joe and Tiffani. (You get the picture.)
And so hypothetically you get brother fighting brother.
It's understandable for nations to defend themselves from aggression.
But I can also understand that brother fighting brother is also wrong.
I can't see how these two aspects can be reconciled. It's a conundrum and I don't have all the answers.