Which submarine is known as the first used in combat?

The Turtle is recognized as the first submarine to be used in combat. This early submarine was designed during the American Revolutionary War and is notable for its innovative, albeit simple, construction. It was intended to attack British warships by drilling into their hulls and planting explosive charges. Its unique circular shape and manual operation set it apart from later submarines.

The significance of the Turtle lies not only in its historical context but also in its pioneering use of underwater warfare tactics. The Turtle represents a critical step in naval advancements, showcasing the potential of submarines in military operations. Through its efforts, it laid the groundwork for future developments in submarine technology.

In contrast, other options represent different important milestones in submarine history but do not hold the same title in combat. The CSS Hunley was the first combat submarine to sink an enemy ship but was not the first to be used in any combat capacity. The USS Nautilus, while being the first operational nuclear submarine, came long after the Turtle and did not see combat in the traditional sense during its early operations. The Submarine Force refers to a grouping of naval vessels and does not specify a single submarine, making it less relevant to the question.