Learning Pearl Harbor: What Is a Dry Dock?

As you explore the fascinating history of the US naval base at Pearl Harbor, specifically the December 7, 1941 Japanese attack that forced the Americans into World War II, you’re bound to come across terms that aren’t commonplace in everyday vocabulary. At least not outside of a naval setting. The exhibits and memorials at the World War II Valor in the Pacific National Monument and associated Pearl Harbor Historic Sites do a great job of making it easy to understand what happened that day, but it's helpful to understand certain terminology.

One term you’re sure to hear—dry dock—refers to a very important element of a naval base and comes up often during discussions about the attack on Pearl Harbor.

What Is a Dry Dock?

HMS Victory in dry dock, Portsmouth, UK

As the name indicates, a dry dock is a facility devoid of water in which a naval vessel can be worked on.

In practice, the dry dock is first flooded with water, which allows the vessel to enter without the need for additional equipment. Once the ship is secured in place, the dry dock is drained and the ship rests on a structure that prevents it from tipping over or moving for the duration of its time in dry dock.

Typically, a ship will enter dry dock when it needs to undergo repairs or maintenance, or while the vessel is under construction. The use of dry docks is said to date back to medieval China, as far back to the 10th century. The first mention of them came from Shen Kuo, a scientist and statesman during the Song Dynasty, in his Dream Pool Essays.

Dry docks were also in use during the Renaissance in Europe. The oldest surviving dry dock was commissioned by Henry VII of England in 1495, and currently houses HMS Victory, the world’s oldest warship still in commission.

The Dry Docks of Pearl Harbor

Pearl Harbor dry docks, 10 December 1941. Pennsylvania shares Dry Dock 1 with Cassin and Downes.

On December 7, 1941, the day of the surprise Japanese attack, several American warships were in dry dock undergoing overhauls or repairs. Among them was one of the eight battleships present at Pearl Harbor: USS Pennsylvania (BB-38).

USS Pennsylvania was sharing a dry dock that morning with USS Cassin (DD-372) and USS Downes (DD-375). While both of the destroyers sustained severe damage from the Japanese bombs, Pennsylvania wasn't hit, although she was badly strafed. Considering the extensive damage done to the battleships moored along Ford Island on Battleship Row, Pennsylvania was lucky to have escaped relatively intact. From her position, Pennsylvania was among the first US vessels to return fire on the incoming Japanese fighters and bombers.