It was an objective of the  attack, which Union forces were denying him during the siege.
It was an objective of the personal attack, which Union forces were denying him during the siege.
Это была цель нападения, в которой силы Союза отказывали ему во время осады.
Это была цель личной атаки, в которой силы Союза отказывали ему во время осады.