The main source of our historical account of the miracle of Chanukah comes from the gemara (שבת כא:): “When the kingdom of the House of the Chashmonaim overpowered and defeated the Greeks, they searched and found one flask of oil that was set aside and sealed with the (private) seal of the Kohen Gadol.” Many Meforshim comment on the enigma of the “seal of the Kohen Gadol” since nowhere do we find that the Kohen Gadol maintained a private seal.    The Bobover Rov, R’ Benzion Halberstam Shlit’a, quotes from the Sefer Bas Ayin who surmises that the seal of the Kohen Gadol was actually a reference to his unique station as the one who wears many articles of clothing (מרובה בגדים) - eight in all. Thus, his seal was the letter "ח" which equals the number eight. For this reason, as well, Chazal established the Yom Tov of Chanukah for eight days, to commemorate the letter "ח" on the flask of oil.     But even more than that, the letter "ח" accurately portrayed the role of the Kohen Gadol. His purpose was to unify the people in the service of the Almighty. The letter "ח" when written by a scribe in the Sefer Torah, is a combination of the letter "ו" and the letter "ז". A tiny bridge connects the two letters (ח) which amount to thirteen, the same as the gematria of the word "אחד" - the symbol of unity.     When the Greek Hellenists entered the Bais Hamikdosh, they performed 13 desecrations (פרצות) which tore apart the nation.  Matisyahu, the Kohen Gadol, and his sons, fought and defeated the evil invaders and by doing so, they unified the people under one banner. Hashem chose to reveal one hidden flask of oil with the symbolic seal of the Kohen Gadol - the unifying letter "ח" which totals 13 - to demonstrate that the miracle of Chanukah was much more than a war victory - it forged the Achdus of Klal Yisroel!