49 A.D., the Jerusalem Christians, under the leadership of James, the brother of Jesus (not the apostle James), called a council to address the objections of Paul and Barnabas to their position that a person could not be saved who was not circumcised. In essence, upon arriving back to Antioch from what is miscalled Paul's "first missionary journey", Paul and Barnabas heard this heresy and got right in the face of those promoting it.
The miraculous deliverance experienced on this missionary journey (recorded in Acts 13 and 14) could not have gone unnoticed by the massive Christian church in Jerusalem, a church in which "a great company of priests were obedient to the faith" (Acts 6:7), a church in which the sect of the Pharisees had at least some say (Acts 15:5), a church which by 57 A.D. had "many tens of thousands who believed (Acts 21:20- myriades should be translated "tens of thousands" rather than "thousands").
Since Paul had no "authority" from the Jerusalem church, it seems they just had to belittle the work that Jesus Christ was doing through Paul. And so, when Paul and Barnabas got back to Antioch upon completion of the mission they had been called to execute, the message awaiting them was "well Paul, what you did was nice, but none of those people became Christian because none were circumcised."
The Epistle to the Galatians is Paul's answer to the "sentence" of James at the Jerusalem council. Paul's answer is, "they who seemed to be somewhat in conference added nothing to me." (Gal.2:6).