A) That the Talmud Bavli Shabbat 21a - 24b describes ONLY the miracle of the Oil in Mai Hanukah - quoting a B'raitto from M'gilat Ta'anit.
B) That the Al Hanissim omits the miracle of the oil entirely
Question: How can we have two authentic sources with such a divergence as to what occurred?
One "Drushy" approach can be found in the Artscroll Book on Hanukkah [page 13]. The same question is raised and the answer proffered there is that of the Maharal; namely that the miracle of the oil confirmed what was only a hypothesis, that the military victory was also due to Hashgachah P'ratit. Without an open miracle, we might have suspected otherwise. The advantage from a Spiritual perspective is "inspiration"
While as a D'rashah, we do not quibble with the Maharal's sentiments, nevertheless we still may wish to continue digging. And because this answer raises many questions of its own, including the absence in other accounts such as Maccabees and Josephus, it makes sense to see if we can find a more historical simplified approach.