How long did the war before Chanukah last?

Answer 1

About three years, until 165 BCE. Note that the war continued after that as well (for over two decades). The events of 165 BCE are what we celebrate because it was then that the Temple was rededicated and the miracle of the oil occurred.

Answer 2

It was about 1 year (166 BCE to 165 BCE), but it is not known if it ended with a Chanukah celebration. In fact, it is more likely that it ended with a belated Sukkot celebration.

Answer:

1) The reference to a "belated Sukkot" is from a non-traditional source. Sukkot is celebrated on time or not at all.

2) Yes, it is known that Hanukkah was instituted immediately after the relevant events, as stated in Megillat Taanit (ch.9), the Talmud (Shabbat 21b), and the Books of Maccabees (I, 4:56-59; and II, 1:18).

3) The relevant war was three years, not one year.