There are two distinct mitzvos that we perform on Chanukah, the mitzvah of hadlakas neiros and the mitzvah of krias Hallel. It is not surprising that Chazal instituted two different mitzvos to commemorate the events of Chanukah, since two miracles occurred that we are celebrating. The miracle of the oil is commemorated by lighting Chanukah candles, whereas the victory of the battle against the Yeavnim is marked by reciting Hallel. Chazal tell us (Megillah 14a) that we recite Hallel when we are saved through a miracle. As great as the miraculous events of the menorah in the Beis Hamikdash were, these events would not cause us to recite Hallel. Only the events of the battlefield preceding the restoration of the Beis Hamikdash should warrant the recitation of Hallel.
Each day of Succos we complete the Hallel, whereas on Pesach we recite an abridged form on Chol Hamoed and the concluding days. Chazal (Taanis 28b) explain that this difference reflects a basic distinction between Succos and Pesach. Each day of Succos is a separate yom tov since the korbanos that are offered each day differ from the previous day. On Pesach the identical korbanos are offered each day, therefore the entire week of Pesach is viewed as one yom tov. Therefore, once a complete Hallel is recited on the first day there is no need to repeat it on subsequent days. Tosafos raises the problem that according to this criterion we should only complete the Hallel on the first day of Chanukah. Why do we view each day of Chanukah as a separate entity? Tosafos concludes that the miracle of the oil was renewed each day. Since each day the oil lasted was a new miracle, we commemorate each miracle with a daily completion of Hallel. The solution of Tosafos seems difficult - since the recitation of Hallel relates to the victory on the battlefield, why is the daily nature of the miracle of the oil relevant? It would seem that the complete Hallel should only be recited once, since we were only saved once.
Although it would appear that the two miracles of Chanukah are distinct from one another, Tosafos obviously viewed them as one. A deeper understanding of the battle between the Chashmonaim and the Yevanim will enable us to understand the relationship between the two miracles we celebrate on Chanukah.
The battle between the Chashmonaim and the Yevanim was fought on two fronts. There was a physical battle fought between armies on a battlefield, and there was also a battle between two ways of life. The hedonistic, impure way of life personified by the Yevanim clashed with the devotion of the Chashmonaim to the pure life of Torah. This dual battle is emphasized in al hanissim. We not only mention the victory of the few over the many, but also recognize the defeat of the impure and wicked at the hands of the pure and righteous.
When the war ended, it was obvious that the Chashmonaim were victorious on the battlefield. However, it was not apparent who had won the spiritual conflict. Perhaps the Chashmonaim had defeated their enemies with their swords, but it still had to be determined who would emerge victorious in the battle between Torah and Yavan. Hashem performed a second miracle that would prove that the spiritual battle had also been won. Chazal associate the light of the menorah with the light of Torah. If pure oil could burn for eight days despite the defilement of the Beis Hamikdash by the Yevanim, the pure light of Torah had emerged victorious from the darkness of Yavan. The miracle of the oil was not distinct from the miracle on the battlefield, but rather it was the completion of the physical struggle that occurred. The Chashmonaim emerged victorious on the physical and spiritual battlefields. Lighting the menorah in the Beis Hamikdash was not just a mitzvah, but rather the victory in the spiritual war. Being saved from spiritual annihilation warrants reciting Hallel just as a physical deliverance does.
Our reciting of Hallel on Chanukah celebrates both aspects of Chanukah. Although for the victory on the physical battlefield it would have sufficed to recite Hallel once, the spiritual victory was renewed each day of Chanukah, thereby requiring a new Hallel on each day. As we recite a new Hallel each day of Chanukah, let us focus on the victory of the renewal of Torah that is the true cause for our celebration.