The Braita quoted in Shabbat 21b describes Chanukah as days of Hallel V’Hoda’ah, interpreted by Rashi as the recital of Hallel and Al Hanisim. The Rambam apparently had a different version of the text describing Chanukah as days of Simcha and Hallel. In both versions however, saying Hallel is an intrinsic part of the observance of Chanukah.
This explains why the Rambam delayed his full discussion of the days when Hallel is recited until the laws of Chanukah, even though he mentioned the obligation of saying Hallel earlier in his code. Since the Rambam understands the obligation to say Hallel to be of rabbinic origin, its recital can’t help to define the biblical holidays, although we say Hallel on each of them. It is clear why lighting the menorah is intrinsic to the definition of Chanukah, but less clear why Hallel should be.
The Rambam introduces his discussion of Chanukah with a historical review of the events that led to the holiday. He describes the anti-religious decrees of the (Syrian) Greeks against the Jews, including their defiling the Temple. The first law concludes with the victory of the Hashmonaim through the mercy of the Almighty, their proclaiming a king from amongst the priests, and the return of Jewish sovereignty over the land of Israel for two hundred years.
The necessity for a second letter establishing the holiday of Purim implies that the initial letter was not fully accepted. Yet it is unclear why not, or what was added in the second letter to permanently establish the celebration of Purim. The only apparent new elements in the second letter are that while the first came from Mordechai, the second primarily came from Queen Esther. Further, a comparison is made between the Jewish people’s acceptance of the fast and their acceptance of Purim.
The Ramban suggests that the Jews were still afraid and needed the authority of the queen to reassure them before feeling free to celebrate. However, there is no explicit mention of any lasting fear. The Ibn Ezra mentions three opinions about the reference to the fasts. The Rambam sees them as a hint to Ta’anis Esther. According to this view, it may be that the victory of Purim had to incorporate the vulnerability that preceded the triumph to be fully approved by the Sages in Israel marking Purim as a galus celebration. This interpretation reflects the Rav’s understanding of the nature of our celebrating of Purim. The permitting of excessive drinking reflects an intensive, but temporary and artificial, high.
In the recital of Al HaNissim on Chanukah we thank Hashem for the many miracles in the military victory of the Chashmonaim over the Greek Syrians who had persecuted the Jews. Rashi’s comment on the question of the Talmud in (Shabbat 21b), mai Chanukah, on which miracle was the celebration of Chanukah based, clearly assumes a focus on only one specific miracle. Our obligation to publicize the miracle is restricted to the miracle of the crucible of oil that lasted for eight days.
Rabbi Soloveitchik explains that when thanking Hashem for the miracles He has done for us, we are required to be expansive. In both the Amida and Birchas haMazon, Al HaNissim is recited within the framework of the blessing thanking Hashem. If one accepts the textual version of this prayer that adds the connective vav in u’vezman hazeh, this expansion is extended to our own times. This concept is demonstrated as well in the Seder night in the later part of the Haggadah.