The term boleshet is related to the Hebrew balash (a detective in modern Hebrew), indicating a close, careful search. A boleshet therefore refers to a group of soldiers or policemen who have come to engage in a search – for people to arrest, smuggled or stolen goods, etc. This mission allows the group to enter anywhere they choose and open whatever they want, even during peacetime.
The Ra’avad explains that even during peacetime, the boleshet has blanket permission to eat and drink from the possessions of the local populace, so we must assume that they have taken wine. If the barrels were closed, however, there is no concern that the boleshet opened them and then closed them, since they have nothing to fear if they just left them open.
According to the Mishna, during wartime, the soldiers do not have time to offer libations so even open barrels are permitted. Nevertheless, shouldn’t we be concerned that the non-Jewish soldiers touched the wine when they took some to drink? Rabbeinu Yona argues that the Rabbinic injunction forbidding wine that was touched by a non-Jew is limited to situations where there is at least a possibility that an idolatrous libation may be offered. Therefore, in a case where the concern about libation is removed entirely – like a situation where the soldiers are engaged in battle – no Rabbinic injunction would be in force.
According to the Mishna on today’s daf, when a boleshet – an army unit – entered the city, during peacetime we are concerned about open barrels of wine but not about closed barrels of wine. During wartime we rule that all barrels of wine are permitted – whether open or closed – since we assume that the soldiers will not have time for libations to their gods, since they are occupied with their fighting.