Theophylact of Ohrid

There was at that time [of the capture of Jerusalem] unendurable tribulation. For the Roman soldiers were commanded to spare no one; but God, for the sake of those who would believe or who had already believed, did not allow them to be completely destroyed, but curtailed both the tribulations and the war. For if war had continued any longer, everyone within would have perished of starvation. Some understand these words to refer to the days of the Antichrist; but they are not concerning the Antichrist, but the capture of Jerusalem. …

Commentary on Matthew ↗

Augustine of Hippo

In Luke it is thus read, There shall be great distress upon the earth, and wrath upon this people, and they shall fall by the edge of the sword, and shall be led away captive into all nations. (Luke 21:23.) And so Josephus, who wrote the Jewish History, (B. J. vii.) relates evils so great happening to this people as to seem hardly credible. …

Catena Aurea by Aquinas ↗

Thomas Aquinas

Hence, the necessity for fleeing? From the magnitude of the tribulation. Hence, first he sets forth the tribulation and its magnitude; secondly, he sets forth the cause, at and unless those days had been shortened, etc. He says, therefore, for there shall be then great tribulation, such as hath not been from the beginning of the world. And this can be sufficiently perceived by one who reads the history of Josephus: that many died of hunger. …

Commentary on Matthew ↗