During World War II, U.S. submarines accounted for approximately what share of enemy shipping?

During World War II, U.S. submarines accounted for approximately what share of enemy shipping?

• A. 25%
• B. 75%
• C. 90%
• D. 55%

Answer: (D)

Submarine warfare against enemy shipping was the decisive pressure point that severed Japan’s supply lines. The best estimate puts U.S. submarines responsible for roughly 55% of Japanese shipping losses—more than half of the merchant marine tonnage Japan relied on for fuel, food, and materials. This level of impact shows how pivotal the submarine force was in crippling Japan’s war economy, even as other Allied services also contributed to sinking ships. The other numbers don’t fit the historical pattern: 25% is too small to reflect the scale of the campaign, while 75% or 90% would overstate the subs’ share, implying an unrealistically dominant role beyond what the records show.

Submarine warfare against enemy shipping was the decisive pressure point that severed Japan’s supply lines. The best estimate puts U.S. submarines responsible for roughly 55% of Japanese shipping losses—more than half of the merchant marine tonnage Japan relied on for fuel, food, and materials. This level of impact shows how pivotal the submarine force was in crippling Japan’s war economy, even as other Allied services also contributed to sinking ships. The other numbers don’t fit the historical pattern: 25% is too small to reflect the scale of the campaign, while 75% or 90% would overstate the subs’ share, implying an unrealistically dominant role beyond what the records show.