USS Spearfish and submarine sea denial

Peacetime submarine work includes training, intelligence, and special-forces support. In war, a boat becomes a mobile sea-denial threat that an opponent must destroy or avoid. Spearfish stands out for sustained American service in the Pacific and twelve war patrols. Her hull was less than one hundred metres long and nine metres wide, yet it had to accommodate roughly sixty sailors. Diesel engines, torpedoes, living spaces, and every other requirement competed for that narrow internal volume. Spearfish's endurance and combat power came with severe limits on space and habitability.