It is Hanukah, and for eight days traditional Jews will add to their prayers - specifically the Amidah and Grace after Meals - the blessing "al ha-nisim. " This blessing thanks God for delivering the Jews from the wicked tyrants who profaned the Temple, that is, the "wicked Greek kingdom" that rose up "in the days of Mattathias son of Yohanan, the Hasmonean high priest, and his sons."
Huh? What was that again?
The grammer of this clause is ambiguous. Who is the high priest here, Mattathias or Yohanan? Does this refer to a high priest who was from the Hasmonean family, or the high priest of the Hasmoneans, whatever that might have meant?
No matter how the clause is taken, though, it is wrong.
According to 1 Maccabees 2:1-5: "At this time a certain Mattathias, son of John (=Yohanan), son of Symeon, appeared on the scene. He was a priest of the Joarib family from Jerusalem, who had seettled at Modin. Mattathias had five sons, John, called Gaddis, Simon called Thassis, Judas called Maccabaeus, Eleazar called Avaran, and Jonathan called Apphus." The prayer seems to cite the very beginning of the passage, but it changed its simple notice of priestly descent into an implication that Mattathias was from the family of the high priest.
In fact, from perhaps the time of David (ca. 1000 BCE; 2 Samuel 20:25) until the Maccabean crisis the high priesthood was not claimed by the Joarib family, but by the family of Zadok. The high priest Onias III was murdered by his brother Jason, who in turn was very soon deposed by Menelaus. While Onias III's son - the aptly named Onias IV - apparently went to Egypt to found another Jewish temple there, it remains unclear if Menelaus is from a different family or was related to Onias III. In 168 BCE Jason attacked Menelaus in Jerusalem, but lost and ended up dying in exile (2 Maccabees 5:5-10). Menelaus held the office of high priest until Antiochus IV tired of his shananigans and in 163 BCE had him executed - or, in the eyes of the pious writer of 2 Maccabees (13:3-8), God gave him the punishment he richly deserved. A certain Alcimus thereafter claimed the high priesthood; the fact that both 1 and 2 Maccabees are hostile to him and yet do not dispute his claim that he had a legitimate right to the position is telling (1 Macc. 7:14; 2 Macc. 14:7). Alcimus was struck down in 159 (1 Macc. 9:54-57).
By now, Judas was dead and his brothers, Jonathan and Simon, were continuing the war. Peace came in 152 BCE, and "Jonathan assumed the vestments of the high priest in the seventh month of the year 160 [=152 BCE] at the Feast of Tabernacles" (1 Macc. 10:21). Coins dating from after 134 BCE show the Hasmonean rulers firmly in control of the position of high priest.
The preservation of the "al ha-nisim" prayer thus, at minimum, illustrates a shaky grasp of history. But this is not very surprising. The prayer probably dates to the early middle ages, and even if the rabbis then had an interest in preserving what we would consider an accurate history - and by all accounts, these early rabbis did not - it is unclear what sources they might have used, even if they had access to them.
More interesting, though, is that although it has been known for centuries that this text is inaccurate, it continues to be recited. Here the realms of history and memory meet; history is subsumed by an ancient, mistaken memory. As remembered, Mattathias and his sons are not usurpers of the legitimate priestly line (even if it might rightly be argued that by the time of Alcimus they hardly deserved that honor), but legitimate claimants to this post, aided by God. To tell the story as it really seems to have happened is also to raise uncomfortable questions about God's role in it.
And that story would just not do on the Festival of Lights.