Modi'in is the historical name of the mountain stronghold of the Maccabeans whose victory over the vastly superior forces of the Hellenist Greek oppressors is celebrated on Chanuka.
In his historical account of that epic struggle between pagan idolatry and Hebrew faith, Josephus describes how the wicked Antiochus ordered his officers to wipe out any trace of Judaism. They did indeed slay anyone who remained faithful to Torah observance, except for those who fled to the mountain area of Modi'in together with Matitiyahu, the son of Yochanan.
It was from this Modi'in that Matitiyahu and his five sons led their small band of faithful Jews in a seemingly hopeless war of "the mighty against the weak, the many against the few, the impure against the pure, the wicked against the righteous, the sinners against those who adhered to the Torah" — a war ending in a miraculous victory, climaxed by the miracle of the oil in the Menora which burned for eight days.
Since the Six-Day War, the Modi'in area has been intensely developed and is the home of the fast-growing city of Modi'in and the large Torah community of Kiryat Sefer.