Two witnesses appear in the city before the Gentiles come to trample it down. The two witnesses are clothed in sackcloth, the traditional garb of those who are sorrowing, especially over sins committed by or for those breaking God’s covenant with Israel. They are reflective of the prophets who have been sent to Israel over the centuries of her existence, and also culminate the fulfillment of Christ’s lament recorded by Matthew and Luke:
Therefore, behold I am sending you prophets and wise men and scribes; some of them you will kill and crucify … that upon you may fall the guilt of all the righteous blood shed on earth, from the blood of righteous Abel to the blood of Zechariah, the son of Berechiah, whom you murdered between the temple and the altar. Truly I say to you, all these things shall come upon this generation. 0 Jerusalem, Jerusalem, who kills the prophets and stones those who are sent to her! (Matt. 23:34-37, cf. Luke 13:33-34 – prophets must die in Jerusalem).
I believe the two witnesses were Moses and Elijah, as evidenced by the miracles they perform. They prevent rain as Elijah did (1 Kings 17-18; Luke 4:25), and send plagues like Moses (Ex. 7f).
Rev 11:6-13 – John mentions several signs that would accompany their prophesying and testimony:
1. Power to shut up the sky so rain will not fall during the days of their prophesying (like Elijah)
2. Power over the waters to turn them into blood (like Moses).
3. Strike the land with plagues (like Moses).
4. At the time of their ascension there was a great earthquake.
5. A tenth of the city fell and seven thousand people were killed in the earthquake.
Based on this description of the two witnesses and the signs they performed, it implies that they were either Moses and Elijah, or someone who performed the same kind of signs that they did. The Jews believed that the bodies of Moses and Elijah were under the control of God, and that He had reserved those bodies for them to appear back in the flesh inside Jerusalem at the End of Days to give their final warning and chance to repent before Israel was destroyed (cf. the apocryphal books of the Assumption of Moses, Book of Enoch, Apocalypse of Elijah, etc.).
In view of the corpses laying unburied in the street of the Great City (Jerusalem) for three and a half days, it seems that this event must have occurred after the revolt began, and after the Zealots had control of the city (AD 68). The Idumeans came into Jerusalem in AD 68 and helped eliminate the moderate leaders and their forces. From that time forward, the three Zealot factions were in control. Their civil strife destroyed all their food supplies, and killed a lot of each other’s forces. There was simply too many corpses to bury, so they threw them over the wall into the valley of Hinnom, or let them pile up in the city.
This story of the two witnesses sounds like it would have happened after the Zealots were in control. The moderates would not have left their corpses unburied in the streets of Jerusalem for three days. But the Zealots would have done that (either Eleazar ben Ananias’, John of Gischala’s, Simon the son of Gioras’ soldiers).
I believe the two witnesses (Moses and Elijah) appeared back in the flesh inside Jerusalem to read the final divorce contract to the Jews and give them their final warning and chance to repent before they were destroyed. It is almost like Moses going into Pharaoh that final time just before the Death Angel passed over to kill the firstborn of Egypt. Rather than heed the message, the Zealots killed the messengers, and then their real troubles began to multiply out of their control. Titus then arrived on the scene and began the final siege.
This also makes even more sense in view of the Transfiguration where Moses and Elijah appeared to Jesus and were “talking with Him and … were speaking of His departure which He was about to accomplish at Jerusalem” (Luke 9:30-31; cf. Matt. 17; Mark 9). We first of all have to wonder why Moses and Elijah appeared to Jesus on the mount, and then also why they were talking to Jesus about his imminent death on the Cross and the other associated events. Some commentaries on the Transfiguration and on this section of Revelation 11 have noted as I already mentioned above that there were pre-Christian Jewish writings (Assumption of Moses, etc.) which taught that the bodies of both Moses and Elijah were kept by God for their use at the End of Days when they would reappear to give their final warning to the Israelites. That really brings these two sections of scripture together and gives them tremendous significance. If this is what Revelation 11 is pointing to, then it means that Moses and Elijah are the two witnesses to whom pre-Christian Jewish writings referred.
It is also worth mentioning in this regard, that according to Yosippon chapter 73, which was written about the horrible conditions inside Jerusalem just before Titus raised the final siege in the Spring of AD 70, the writer of Yosippon (supposedly Joseph ben Gorion, who was one of the acquaintances of Josephus) bemoans how the city and temple were completely polluted with the dead corpses laying everywhere unburied. He calls upon Moses, Aaron, Joshua, David and Elisha to awake out of Sheol and intervene on behalf of the Jewish people. If Moses and Elijah did come to Jerusalem at this time, and I believe they did, it was not to help the Jews, but rather to warn them to repent, or else be destroyed.
Conclusion
So, it seems to me that sometime during the final two years of the revolt (AD 68-70), when the Zealots were killing each other in the streets of Jerusalem and leaving the corpses unburied, would have been the most likely time for the Two Witnesses (Moses and Elijah) to have been giving their final warning and then be killed and their bodies be left unburied in the streets. According to Yosippon, it was at this very time when he composed this dirge appealing to Moses and the prophets to reappear and do that very thing. Evidently Moses and Elijah did appear, but the people rejected their warning and killed them instead. That sealed their doom. Titus immediately raised the final siege against Jerusalem.
Related full “Study Series” (available upon request if not hyperlinked):
[For a more in-depth study see eschatology “Study Series 16 Lesson 3 Rev. Chapters 10 thru 12”]