Paul worked for around 14 years in a hidden way far away from Jerusalem. He preached the gospel that had been revealed to him. While he laboured he continued to receive revelations regarding the gospel. At the same time he also suffered while spreading the word of the gospel in the regions of Syria and Cilicia (modern day Turkey). Yet Paul worked in a hidden way, not trying to gain a name for himself but being faithful to the commission given him by God.  

Fourteen years later he went to Jerusalem with Barnabas and Titus, most likely to bring money for the poor in Judea. Here he presented what he was preaching and how Gentiles were responding to the gospel. The leaders in Jerusalem had nothing to add to what Paul was preaching. This confirmation by the Jerusalem apostles should have given the Galatian believers confidence in the gospel Paul was preaching.  

However, there were people in Jerusalem, false brothers, who wanted to impose Jewish observances such as circumcision upon the Gentile believers in order for them to be received into the people of God. Paul strongly objected to this so that the truth of the gospel would be preserved especially for the gentile believers.