1,364. Troubles Caused by Enemies; Passing Soldiers

Hilchos Taaniyos 2:3

Troubles caused by our enemies (in halacha 2:1) includes when they come to wage war, impose a tax, take away land, or pass a decree prohibiting even a minor mitzvah. In all of these cases, we fast and sound trumpets until God’s mercy arrives. Residents of the surrounding cities should also fast but they don’t sound trumpets unless necessary to gather the people to come to their aid.

Hilchos Taaniyos 2:4

An armed regiment passing though (again, in halacha 2:1) refers even to one that comes in peace - for example, if two nations were warring with one another and the soldiers passed through a Jewish community. Even though they are not at war with the Jews, it is nevertheless considered a time of trouble for which we fast as per Leviticus 26:6, “A sword will not pass through your land.” We see from this that simply seeing war is a sign of trouble.