Some 2100 years ago the Land of Israel came under the rule of the Syrian-Greek emperor Antiochus, who issued a series of decrees designed to force his Hellenistic ideology and rituals upon the Jewish people. He outlawed the study of Torah and the observance of its commands, and defiled the Holy Temple in Jerusalem with Greek idols.
A small, vastly outnumbered band of Jews waged battle against the mighty Greek armies, and drove them out of the land. When they reclaimed the Holy Temple, on the 25th of Kislev, they wished to light the Temple’s menorah (candelabrum), only to discover that the Greeks had contaminated virtually all the oil. All that remained was one cruse of pure oil, enough to last one night—and it would take eight days to procure new, pure oil.
Miraculously, the one-day supply of oil lasted eight days and nights, and the holiday of Chanukah was established.
To commemorate and publicize these miracles, we light the Chanukah menorah (also known as a chanukiah) on each of the eight nights of Chanukah. This year, we start lighting the menorah on Saturday night after nightfall, December 8, 2012.