Paul wrote the letter to the Galatians to defend his apostolic authority and the true gospel message of salvation by faith alone in Christ. Some false teachers had been influencing the Galatian churches to believe that Gentile converts must be circumcised and follow Jewish laws to be saved. Paul strongly defends his divine calling as an apostle and emphasizes that salvation comes solely through God's grace as revealed in Christ's death and resurrection, not by works of the law. He expresses deep concern that the Galatians have deserted the true gospel.