Why did both sides begin to use conscription early in the war?

Both sides began to use conscription early in the war due to the need for a larger and more sustained military force to meet the demands of prolonged conflict. As battles intensified and casualties mounted, volunteer enlistments were insufficient to maintain troop levels. Conscription allowed governments to ensure a steady supply of soldiers, enabling them to field larger armies and maintain their war efforts effectively. This shift reflected the recognition that a total war approach required comprehensive mobilization of society's resources, including its manpower.