Why did German U-boats begin using snorkels during World War II?

German U-boats began using snorkels during World War II to address a critical operational vulnerability: the need to surface to recharge their batteries.

Submarines of that era relied on internal-combustion engines to power the generators that recharged their propulsion batteries. Because these engines required air to function, U-boats were forced to surface, which exposed them to detection by Allied radar and aircraft.12

By utilizing a snorkel—a ventilating tube raised while the vessel cruised just beneath the surface—U-boats could intake air and exhaust engine fumes while remaining submerged. This allowed them to recharge their batteries without surfacing, effectively transforming them into more capable submarines that were significantly harder to detect. While this innovation reduced the effectiveness of Allied radar, it was introduced late in the war and ultimately could not overcome the overwhelming Allied air and surface resources.13