Its story
'Judaizers' is the name Christian tradition gave to those in the Church's first generation who insisted that non-Jewish believers be circumcised and keep the Mosaic Law (Sabbath, food laws, calendar) in order to be true disciples of Jesus. They were not an organized sect with a founder but a current within Jewish-Christian communities. The Greek verb ioudaïzein ('to live like a Jew') appears in Galatians 2:14.
The conflict arose as the gospel spread to Gentiles. Acts 15 reports that 'some men came down from Judea' to Antioch teaching that without circumcision there was no salvation, and that the question was taken to the apostles and elders in Jerusalem (c. 49). The meeting, at which Peter and James spoke, concluded that circumcision should not be imposed on Gentiles, though they were asked to abstain from certain practices (Acts 15:28–29). Galatians, with its forceful defense of justification by faith and not by 'works of the Law', reflects Paul's side of the same dispute; scholars debate exactly how Galatians 2 relates to Acts 15.
These opponents should be read with nuance: almost everything known about them comes from their critics (Paul and Luke), and their position had understandable roots in Israel's Scriptures, where circumcision is the sign of the covenant. After the fall of Jerusalem in 70 and the growth of largely Gentile churches, the issue faded. Early in the second century Ignatius of Antioch still warns that it is 'absurd to speak of Jesus Christ and to Judaize' (Magnesians 10).
The debate has a modern echo in Pauline studies: the 'New Perspective on Paul' (E. P. Sanders, J. D. G. Dunn, N. T. Wright) argues that the controversy was chiefly about identity markers separating Jews and Gentiles, while more traditional Catholic and Protestant readings see it as a debate about merit and grace. The traditions therefore read differently what was really at stake.