Hanukkah is described in the Talmud. The Talmud (Shabbat 21), in
a discussion concerning Shabbat candles, mentions also the Hanukkah
candles and says that after the forces of Antiochus IV had been
driven from the Temple, the Maccabees discovered that almost all of
the ritual olive oil had been profaned by the Greeks. They found
only a single container that was still sealed by the High Priest,
with enough oil to keep the menorah in the Temple lit for a single
day. They used this, yet it miraculously burned for eight days (the
time it took to have new oil pressed and made ready).
The Seleucids (Syrian-Greeks) under Antiochus Epiphanes (2nd
century BCE), at the instigation of the Hellenizers, had forbidden
various Torah-practices such as Sabbath-observance and
circumcision, rededicated the Temple to a Greek idol, and pressed
the Jews to offer up sacrifices to the idol. One of the leading
elder Jewish sages called upon the people to keep observing the
Torah anyway; and if necessary, to use force in resisting the
decrees. When a Hellenized Jew offered a sacrifice to the Greek
idols in a nearby village, the sage killed him as well as the Greek
overseer. This brought a violent reaction from the Greeks; and the
loyal Jews, led by the Hasmonean family, were forced to retreat
from their towns and strike out at the Greeks in an attempt to oust
them from the Holy Land and to enable the people to once again
observe the Torah. The Torah-Jews were heavily outnumbered by the
attacking Greek armies, but God gave them miraculous victories
again and again. After three years of struggle, the Greek armies
retreated from Jerusalem, and the Hasmoneans (also called
Maccabees) entered the Holy Temple which the Greeks had defiled,
reconsecrated it to God, and began the Temple service once more.
Among other things, they wanted to relight the olive oil
candelabrum (Exodus ch. 25), but could only find one day's supply
of undefiled oil - and it would take eight days to make and bring
Miraculously, the menorah stayed lit for eight days (Talmud,
Shabbat 21b), allowing enough time for new oil to be prepared and
brought. The significance of the miracle is that it demonstrated
that God's presence was still there. The Torah-community was
overjoyed, because God's presence meant everything to them.
This is what Hanukkah represents: the closeness to God; and the
avoidance of Hellenization (assimilation).
The Torah Sages instituted the festival of Hanukkah at that time
(Talmud, Shabbat 21b), to publicize the miracle (Rashi commentary,
ibid). This is why we light our Hanukkah-menorahs.
(The Hanukkah-menorah, or hanukkiyah, is a special form of the
original seven-branched menorah. Our Hanukkah-menorahs have eight
spaces for oil, or candles, to mark each of the eight days for
which the oil lasted and a ninth to hold the shamash, a candle used
to light the others.)
The Al-Hanisim prayer which we recite during Hanukkah centers
around the Hasmoneans' victory and rededication of the Temple,
while the candle-lighting commemorates the miracle of the oil.
Though the military victory is prominently mentioned in the
prayers, it wouldn't have been celebrated if not for the miracle of
the oil. It should also be noted that the main goal for which the
Maccabees fought was not political independence. They fought to
enable the people to observe the Torah's commandments; as we say in
the Al Hanisim prayer: "The Greeks sought to cause us to forget
Your Torah and leave Your statutes."