τότε οἱ ἐν τῇ Ἰουδαίᾳ φευγέτωσαν εἰς τὰ ὄρη,As a military strategy, fleeing to the mountains had already been successful on at least two different occasions in Israelite history. Once under Joshua when Israelite settlements were almost always in the hills. The second time was under the Maccabees. The latter seems to be the historical precedent to which Jesus refers.
Then, let those in Judea flee to the mountains. (Matthew 24:16–17)
The idea is to get away from Jerusalem, which was corrupt. The idea partially backfired at Masada. Masada was partially successful because the place was defensible and the Romans had to lay siege for a couple of years. The Romans won in the end but the victory was very costly. One cannot think of what the Romans did at Masada and not think of the words of Tacitus (Agricola 98):
ubi solitudinem faciunt, pacem appellant
They make a desert and call it peace.
