Two Superpowers with a friendly relation

Not really sure if this belongs in here so feel free to correct me.

So this is my first thread, i hope this goes well. Anyway, we all know about the US-Soviet relations in the cold war. And centuries before that there was the Roman-Carthaginean relations.

My question is: had there been a moment in history when two superpowers not only tollerated each other, but were actively friendly with each other. Or if there isn't any then what circumstances could realistically lead to it.

This can range from "direct allies" to simply "aligned interests". And their relation MUST be sustained for a reasonably long period of time. Last and most importantly, they MUST be of comparably similar power/influence/economy/etc. Basically each can (almost) equally harm the other. Of course this would eliminate situations where the two are far enough from each other (for the time period) that they would have no real rason to be antagonistic to each other (thus technically leading to this situation)
 
Britain and the US, 1939-1942. Arguably 1900-1945 too, it just depends on whether you think that both parties had the military strength to be regarded as superpowers over the wider range - US military strength and occupied territory was greatly inferior to Britain's at the start of the twentieth century, while you could say that the fall of Singapore broke Britain as a superpower even before her complete eclipse militarily and financially at the end of the war.

The reason is settled borders, common culture and a powerful external enemy.
 
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