I believe Grant's ultimate goal was to fully encircle Petersburg and Richmond if Lee had stayed put. If the fort or structure is evacuated before the full encirclement occurs, then how would/should it be referenced? Thanks,My definition in the glossary of A Legacy in Brick and Stone: "Siege: The protracted taking of a fort, beginning with investment and continuing through the breaching and ultimate reduction of the work. By the time of the Third System, it was understood that ultimately no fort could hold out indefinitely to a siege." This glossary applies to the Third System of American Coastal Forts, 1816-1867, and is built on D. H. Mahan's Treatise on Permanent Fortifications, Scott's Military Dictionary, and other period sources. I hope this helps!