Paul is concerned about what will happen if the Jerusalem leaders do not recognize Gentile converts as true believers.1 He is worried that his church planting efforts in Gentile areas will be nullified if the Jerusalem leaders agree with those who want to see the Gentiles circumcised.2 They may be tempted to do so because their ministry in Judea consisted primarily of Jewish converts and many of these converts were eager to see the Gentiles following Jewish practices.3
2 I went up because of a revelation and set before them (though privately before those who seemed influential) the gospel that I proclaim among the Gentiles, in order to make sure I was not running or had not run in vain.