But whenever you see Jerusalem surrounded by armies, then know that her desolation has drawn near.
Luke 21:20
This has a dual fulfillment. The question the disciples asked in context here in Matthew would primarily be about the first fulfillment. This first fulfillment was in AD 70 when the armies of Rome destroyed the Temple in Jerusalem.
The future fulfillment will come when there will once again be armies around Jerusalem. These will be the armies of the Antichrist which will desecrate the temple in the time of the end.
Heavenly Father, thank You for telling us about the future. Your Truth in Your Word is a great comfort to our hearts and minds. All our lives we will turn to the pages of Scripture and find glorious things that bring blessing and joy to our lives. In the Name of the Lord Jesus Christ I pray and praise You, Amen.