What event led to the passage of the Conscription Act?

The Conscription Act, passed in 1863, was primarily driven by the Union's escalating need for soldiers as the Civil War progressed. Early in the war, volunteers filled the ranks of both the Union and Confederate armies, but as the conflict dragged on and casualties mounted, it became clear that relying solely on voluntary enlistment was insufficient to maintain troop levels. By instituting a draft, the government sought to ensure that enough soldiers were available to meet military demands, especially after significant battles and the heavy losses suffered by Union forces. This act marked a significant shift in military policy, reflecting the urgency of the situation and the commitment to seeing the war through, highlighting the growing manpower needs as the war intensified.

The other choices focus on specific events that, while significant in their own right, do not directly relate to the fundamental reason behind the passage of the Conscription Act.