Q on Men of the Great Assembly [duplicate]

Question

When did the Men of the Great Assembly start and cease to function and why?

What was their relationship to the Sanhedrin and to beit Hillel and Shammai?

Answer 1

End of first exile to early second temple era.

Begining The Gemara Megillah 2a says that they were involved in instituting Purim and the Gemara there (17b) says that their ranks included some prophets which means that they existed by the end of the first galus (exile). They dont seem to have existed much before that because the first mishna is avos writes that the Anshei Kneses Hag'dolah received the tradition of the prophets. From this and the previous source it seems that they only began at the very end of the period of the prophets, and that the end of the first exile would mark their beginning.

End The second Mishna in Avos writes that Shimon Hatadik was one of the last members and he lived in the second Temple era. More specifically the Gemara (Yoma 69a) says that he met Alexander the great which would place him in the 4th century BCE; this was the beginning of the second Temple era. Thus it seems that according to the traditional reckoning they lasted only from the end the first exile to the beginning of the second Temple.

Sanhedrin: the fourth Mishna is Avos lists Yosi Ben Yoezer as a student of Antignos, student of Shimon Hatzadik. He was a member of the zugos who ran the sanhedrin. The Sanhedrin probably preceded them though and existed at the time of the Anshei knesses hag'dolah.

Beis Hillel / Shammai were the academies of Hillel and Shammai. Hillel and Shammai lived a couple hundred years later in the first century BCE to first century CE.

Answer 2

I'll get this one started: it started with the building of the Second Temple -- ~2500 years ago. It ended in the times of Shimon HaTzadik, who was a contemporary of Alexander the Great.

I don't know enough about why/how it disbanded.

Rambam's introduction to his Yad Hachazaka:

ז בית דינו של עזרא, הם הנקראין אנשי כנסת הגדולה. והם חגיי זכריה ומלאכי, ודנייאל חנניה מישאל ועזריה, ונחמיה בן חכליה, ומורדכיי, וזרובבל; והרבה חכמים עימהם, תשלום מאה ועשרים זקנים. האחרון מהם הוא שמעון הצדיק, והוא היה מכלל המאה ועשרים, וקיבל תורה שבעל פה מכולן; והוא היה כוהן גדול, אחר עזרא.

ח אנטיגנוס איש שוכו ובית דינו קיבלו משמעון הצדיק ובית דינו, ויוסף בן יועזר איש צרידה ויוסף בן יוחנן איש ירושלים ובית דינם קיבלו מאנטיגנוס ובית דינו, ויהושוע בן פרחיה וניתאי הארבלי ובית דינם קיבלו מיוסף ויוסף ובית דינם, ויהודה בן טבאי ושמעון בן שטח ובית דינם קיבלו מיהושוע וניתאי ובית דינם. שמעיה ואבטליון גרי הצדק ובית דינם קיבלו מיהודה ושמעון ובית דינם. והילל ושמאי ובית דינם קיבלו משמעיה ואבטליון ובית דינם. ורבן יוחנן בן זכאי ורבן שמעון בנו של הילל קיבלו מהילל ובית דינו.

The era of the Men of the Great Assembly was succeeded by the era of Sanhedrins; each Sanhedrin was headed by a pair -- zug -- of two rabbis. Hillel and Shammai were at the end of this era of "pairs." Many debates were later held not by the two of them individually, but by their respective academies of students.