When the Gemara in Masechet Shabbat 21b talks about Chanukah, it mentions only the miracle of the oil and not the miracle of the Chashmonaim winning the battle against the Greeks. Why is the miracle of the oil the only one mentioned? Isn’t the miracle of the battle significant too?
Some Acharonim offer an explanation. They say that during the time of the Chashmonaim, the miracle of the battle was celebrated, but after the Chashmonaim died out, only the miracle of the oil remained. After the Beit HaMikdash was destroyed, the focal point of the Chanukah celebration became the miracle of the oil and not the miracle of the battle.
Other Rabbanim give another explanation. The one jug of oil that the Chashmonaim found when they entered the Beit HaMikdash symbolized that even though the Greeks had tried to squash all of the Judaism out of Bnei Yisrael and Hellenize them all, they hadn’t succeeded. This is an important message for us. When we are in Galut, we see many things that may turn us away from Judaism and cause us to assimilate. When we light the Menorah, we remind ourselves who we really are and that we need to remain true to the Jewish faith. This is why we celebrate the miracle of the oil even when times are dark for us like at the time of the Chanukah story. All we need to do is look at the Menorah and remember to remain strong and preserve what faith we have in us. If we keep this faith we shall merit seeing the lighting of the Menorat HaZahav in the Beit HaMikdash.