Chanukah means resting
One of the earliest answers to this question is quoted by Rabbi Nissin Ben Reuven (1320-1376) the RaN. The explanation requires breaking up the word Chanukah. The first part of the word is chonu, translated to mean rested or settled. The final two letter of the word Chanukah are chof and hei. Their numerical value is 25. This would then mean, that the Jews settled from the battle with the Greeks, on the 25th day of Kislev(name of the third Jewish month).
[A simple challenge to this approach would be a historical one. There is a dispute regarding the date the victory over the Greeks took place. Rabbi Moshe Ben Maimon (1135-1204) the Rambam is of the opinion that it took place on the 25th of Kislev. Rabbi Menachem Meiri (1249-1306) the Meiri holds that it was on the 24th. Obviously the opinion of the Ran would not work according to the Meiri.]
The reason for focusing on the winning of the war – over the miracle of the oil lasting for eight days, can be explained very simply. The winning of the war seems to have far reaching effects, mainly, many Jewish lives were sparred. As opposed to the miracle of finding the oil, were although it was a fascinating miracle, it still pales in comparison to the saving of lives.
Is the winning of the war really the theme of Chanukah?
Rabbi Yehudah Loew (1520-1609) – the Maharal offers a beautiful explanation:
“The essence of the establishment of the [holiday of the] days of Chanukah was the defeat of the Greeks, except that it wasn’t apparent to them that this victory was a miracle…therefore the miracle of the lights of the Menorah was done for them so that they would know that everything was a miracle from G-d…”
Numerous small nations have overpowered those stronger then them. The North Vietnamese gave major blows to the “all powerful” United States of America. Afghanistan defeated the great Soviet Union. Almost one hundred years ago, the Irish – few in numbers and poor – kicked the British out of (what is now southern) Ireland despite England’s proximity, wealth, great power status and huge army.
Guerrilla warfare can be highly successful against much larger foreign regimes.
The Jews after winning the war might have been feeling quite accomplished. They fought good and hard. They won the war.
G-d showed them the miracle of the oil. Oil that only had the ability to last one day lasted for eight. G-d’s normally concealed presence came to the open. The miracle lasted not for one day, but for eight days.
The Jews got the message. G-d is always present, not just during the totally radical miracles – but always. The war they thought they could take credit for was really to G-d’s credit. They were just pawns. G-d is the general.
The name of Chanukah, the point of Chanukah, is to bring G-d’s light everywhere. G-d’s light affects all aspects of our life. He is in all our affairs and struggles.
 Tractate Shabbos 22b in his comments on the Rif 21b, quoted in the name of “yesh omrim” (there are those that say).
 Rambam 3,2 cf. and others
 In his commentary on Tractate Shabbos 21b, Rabbi Shneur Zalmen of Liadi Alter Rebbe Torah Ohr end ofParshas Vayeishev and all the Chabad Rebbeim follow with this position.
 This is especially according to the opinions that the impure oil was allowed to be used. The usage of “pure” oil was merely a stringency, see Rabbi Shmuel Eidels (1555-1631) the Maharsha to Tractate Shabbos 21b.
 Ner Mitzvah pg. 22