The issue of whether or not to circumcise Gentile believers led to the first church council, establishing as I think it did a precedent for leaders to gather to discern the mind of God, and a ruling that Gentile converts needed to show some respect for Torah observance. (Incidentally, time wore this ruling down for Gentile Christians and I take this issue up in The Blue Parakeet: Rethinking How You Read the Bible.) After this event, Paul and Barnabas deliver the letter to the church at Antioch.

Acts 15:35 But Paul and Barnabas remained in Antioch, and there, with many others, they taught and proclaimed the word of the Lord.

A brief note today: Paul’s message was “the word of the Lord”. It was verbal; it was about Jesus Christ as Lord. Paul’s gospel is no different, then, than the message of Peter and the early Christians for whom the gospel was “Jesus is Lord.”
It can be inferred, but it is no more than an inference, that “Jesus is Lord” means “Caesar is not Lord.” But the big point I’d make is this: Caesar is only one of the many, many “lords” who cease to be “Lord” when “Jesus is Lord.” So, I take this to be as anti-empire as it is anti-everything-else-that-could-be-Lord.
More importantly, I think, is to see in “Jesus is Lord” a comment that the Lord who was anticipated in the OT and the Lord is who is seen in the OT, namely YHWH, is Jesus.