Vulnerability of Pearl Harbor in 1941

In 1925, Gen. Billy Mitchell published a report called Winged Defense revealing the vulnerability of Pearl Harbor to a surprise air attack.

[2] Shortly after taking office, Navy Secretary Knox wrote an overview memo which specifically noted the possibility of an attack at Pearl Harbor.

"[4] Richardson believed stationing the fleet in Pearl Harbor made the ships extremely vulnerable against attack and provided a poor and unstrategic defense.

The Royal Navy had used Swordfish torpedo biplanes, and their low speed was part of the reason the Taranto attack succeeded.

Due to the shallow anchorage (which continues to require regular dredging), installation of torpedo nets would have severely restricted the mobility of vessels in the harbor.

Pearl Harbor as viewed by Japanese planes during the attack
Battleship Row at Pearl Harbor after the attack
British ship with deployed torpedo nets during WWII