After the Maccabeans destroyed the Seleucids, a group of Gentiles grouped up and tried to destroy the Jews. They did not succeed. The Jews killed many of them and completely disbanded their group.
After the Maccabeans destroyed the Gentiles that gathered against them the Assembly of Israel determined that every year at that season, the days of dedication of the Altar should be observed with joy and gladness for eight days, starting on the 25th of Kislev. Those eight days are called Chanukah. The way that they celebrated Chanukah was eating, drinking, and offering burnt sacrifices for eight days.