The popular view is that it was the Syrian-Greeks who were the enemy. Their campaign to uproot freedom of worship had to be countered. Jews had to be able to be Jews and to worship in the Temple without facing idols and impurities.
But this is not the whole story. There was also an enemy from within, the mit’yav’nim – the Jews who tried to make themselves out to be Greeks and to ape the ways of Yavan. This Hebrew name for Greece derives from Yavan, the fourth son of Yefet (Gen. 10:2, 4), who settled in Greece. Daniel calls Alexander of Macedonia the king of Yavan (Dan. 8:21, 10:20, 11:2). “Yavan” gave rise to the names Ionia, Ionic and Ionian. The Jewish mit’yav’vim acted like Y’vanim; an analogous word is found in the M’gillah, where we read, v’rabbim me’ammei ha’aretz mit’yahadim, “Many of the people of the land acted like Jews” (Esther 8:17).
What is wrong with acting like Greeks? It depends on whether it was, in Cecil Roth’s words, clean or unclean assimilation. Clean assimilation means taking part in the best movements in culture, and adopting the idiom of the time in language, clothing and material civilisation.
Unclean assimilation is the attempt at blurring or effacing one’s Jewish identity, abandoning one’s Jewish name and becoming Jason or Menelaus, playing Greek games naked (the word “gymnasium” comes from gymnos, nude) and trying to obliterate the evidence of being circumcised, eating forbidden food and making obeisance to heathen deities. This was chukkat ha-goy, the worst form of adopting gentile customs (Lev. 18:3, 20:23; Deut. 12:30).
The parameters of chukkat ha-goy are set out in Rabbi Isserles’ glosses to the Shulchan Aruch (Yoreh De’ah 178:1). It is not the mere adoption of neutral social usages or fashions which is the problem, he says, but the acceptance of practices which are based on paganism and/or immodesty and immorality. This would, incidentally, preclude Jews from following Xmas practices which have (or originally had) a religious symbolism. It would also preclude Jews from attempting an amalgam of Chanukah and Xmas, including the bizarre idea of having a Chanukah tree or a Father Chanukah. Jews should not feel they are missing out by having no Xmas. Their own Jewish calendar has ample occasions for colour and celebration.
The Maccabean, and Jewish answer, to mit’yav’nim is the proud declaration of Mattityahu and his family, “Though all the nations that are under the king’s dominion obey him and each one falls away from the religion of their fathers, yet will I and my sons and my brethren walk in the covenant of our fathers” (I Maccabees 2:19-20).