The Bolian front was a theater in the Dominion War.

In 2375 Weyoun received word that the Federation's Sixth Fleet had withdrawn from this front, and wondered what the Federation was planning. (DS9: "Penumbra")

This was some time after "Tears of the Prophets", in which there was established that there were two fronts, the second being the recently opened Romulan front. Therefore, the Bolian front might have been the original front, or a different one opened up later. Starfleet was already conducting a significant operation called the Bolian Operation early in the war as of "Behind the Lines".