Do you know the difference between a submarine and a submersible? A submarine is a watercraft that is capable of independent operation under the sea. Submarines do not require support ships because submarines can renew their air and power supplies independently. Submersibles also submerge and operate underwater, but they need the support of a larger vessel. Submersibles cannot renew their air and power supplies without support. For this reason submersibles are usually smaller and cannot spend as much time underwater as submarines.

The first documented submersible was constructed in 1620 by Cornelius Drebbel. It was powered by rowing oars underwater. Though this craft was originally designed for underwater exploration, it did not take long for inventors and makers of war to recognize the military potential of the submersible. In 1648 Bishop John Wilkins wrote, “It may be of great advantages against a Navy of enemies, who by this may be undermined in the water and blown up.” Over one- hundred years later, the first military submarine was ready to be deployed.

The Turtle was the world’s first submarine used in combat. Designed by David Bushnell in 1775, it was deployed by the Continental Army during the American Revolutionary War. Though the Turtle did utilize a support ship in combat, it was fully capable of renewing its air and power supplies independently; therefore, the Turtle is considered to have been a submarine and not a submersible. The Turtle was powered by hand-cranked propellers and was named as such because it resembled a turtle. It held a single person, moved about three miles per hour in calm water, and contained enough air to stay submerged for about thirty minutes. General Washington authorized an attack using the Turtle on a British flagship blockading New York Harbor. Sgt. Ezra Lee operated the Turtle and attempted to affix underwater explosives to the British ship, but he failed. The Turtle was later destroyed by the British. Despite this failure, the Turtle is still remembered as the first submarine used offensively during war.

Another notable submarine originally designed for war was Julius H. Kroehl’s Sub Marine Explorer. Built between 1863 and 1866, this submarine was created for the North during the American Civil War but the war ended before it went into use. After the war it was used commercially to harvest pearls in Panamanian waters during the late 1860s. Unfortunately, the dangers of decompression sickness (a condition that occurs when divers rise to the water’s surface too quickly) were not understood. While experimenting with the Sub Marine Explorer in 1867, Kroehl himself perished from decompression sickness. In 1869 a new engineer put the Sub Marine Explorer back to the task of harvesting pearls. Tragically, use of the Sub Marine Explorer was discontinued after the entire crew died from decompression sickness.

Submarine use increased greatly during World War I. Due to innovations in engineering, such as a dual power system using both diesel and electric sources, submarines had finally developed into effective war machines. One watercraft called the U-Boat was put to great effect by the Germans. Some argue that the U-Boat was more of a submersible, since U-Boats operated primarily on the surface using diesel engines and submerged only occasionally to attack using battery power, but the effectiveness of the U-Boat in combat is certain. During World War I more than 5,000 Allied ships were sunk by U-Boats, including the Lusitania, which is often cited as a reason why America entered the war.

U-Boats were again utilized extensively by the Germans during World War II. Though the U- Boats were devastating to British fleets, advances in technology such as radar and sonar reduced their overall effectiveness. Additionally, the U.S. had also developed and deployed a fleet of submarines to great effect. Though the Japanese attack on Pearl Harbor destroyed or severely damaged many of the U.S. Navy’s front-line Pacific Fleet ships, U.S. submarines survived the attack and went on to cause great damage. Submarines, though only about 2 percent of the U.S. Navy, destroyed over 30 percent of the Japanese Navy. This made U.S. submarines the most effective anti-ship and anti-submarine weapon in the entire American arsenal.

Modern submarines are now powered by a nuclear reactor. The nuclear reactor generates a tremendous amount of power and frees the submarine from the need to occasionally surface. The large amount of power generated by these reactors allows submarines to operate at high speeds for long durations. Current nuclear submarines never need to be refueled throughout their 25-year life-spans. The only factor limiting the amount of time that an advanced submarine can remain submerged is the amount of food and water that the submarine can carry. Even the Bishop John Wilkins, when he imagined the military capabilities of future submarines from 1648, could not have envisioned such an amazingly powerful watercraft.