During which conflict were submarines first deployed in battle?

The first effective deployment of submarines in battle occurred during the Civil War, particularly with the Confederate submarine, the H.L. Hunley. This submarine became the first in history to sink an enemy warship, the USS Housatonic, in 1864. The H.L. Hunley utilized a torpedo attached to a spar to achieve its objective, marking a significant shift in naval warfare tactics.

Submarines had been conceptualized earlier but the Civil War represented their first true operational use against active combatants. This historical context highlights the groundbreaking nature of the Hunley's mission, which paved the way for the eventual development of more advanced submarine technology in the following conflicts.

While World War I and World War II saw the significant use of submarines with enhanced technologies and tactics, it was during the Civil War that submarines first entered the realm of battle, thus establishing their role in naval warfare.