Submarines are one of the most effective elements of the world's most powerful navies. From sinking shipping during wartime to covert reconnaissance and use as nuclear deterrence, these machines are both feared and admired.
But this wasn't always the case.
Far from a recent invention, submarines have a long and interesting history. The development of submarines was, like many other types of machines, a process of incremental improvements over many centuries.
What are some of the main milestones in the history of the submarine?
And so, without further ado, here are some of the major milestones in the history of the development of the modern submarine. This list is far from exhaustive and is in no particular order.
1. Allegedly, one of the first "submarines" was used by Alexander the Great
Legend has it that Alexander the Great once used a submarine-like structure to study fish. Supposedly, this event occurred sometime around 332 BC, when Alexander was lowered underwater in a large glass barrel.
This device was, technically speaking, a diving bell and not a submarine, but it is one of the earliest recorded uses of the concept. The legend has come down to us through a Persian epic poem that later inspired artists in the medieval period.
Whether or not this event actually occurred is unknown, but it does demonstrate that people have dreamed of exploring the deep using submersible craft for many millennia.
2. Leonardo da Vinci may have designed an early submarine
Renaissance man Leonardo da Vinci may well have produced written plans for an early submarine in around 1515. Recorded in one of his notebooks, now known as the Codex Leicester, his "ship for sinking another ship," resembles, conceptually at least, a modern submarine.
By studying the mechanics of how fish swim, da Vinci theorized that it might be possible to float underwater for an extended period of time. His notes also include information about how the device might be used if it were ever developed.
Da Vinci clearly states that he doesn't want to reveal his plans for the vehicle, "because of the evil nature of men." He feared, rightfully so given the events of later history, that such a vessel could be used to sink enemy ships -- thereby killing their occupants.
3. A former English gunner turned innkeeper may have also invented an early submarine
Less than 100 years later, English mathematician and naval writer William Bourne, turned to the study of inventions for use in warfare. In his 1578 work "Inventions and Devices," Bourne describes the principle of a sinkable boat that can rise and sink repeatedly by changing the ship's volume.
Bourne's design consisted of a wooden frame covered with waterproof leather. It could be submerged by contracting the sides through the use of hand vises, reducing its volume. By expanding the sides, the ship should then, on theory, be able to rise once again to the surface.
While Bourne never built a working model of his vehicle, it presented an interesting idea for how to navigate underwater.
4. One of the first powered submarine concepts appeared in the 1600s
Around half a century later, a Dutchman called Cornelius van Drebbel made the leap of adding a form of propulsion to a submersible vessel. His concept vehicle, called the Drebbel 1, is commonly held to be one of the first "true" submarine designs.
In addition, according to historical records, a test vessel was built and tested on the River Thames in the mid-1620s.
It consisted of an enclosed rowboat, powered by 12 oarsmen, with, it is believed, a sloping foredeck. Working a bit like an airplane wing trimmed for descent, in theory, this would have forced the boat underwater as the forward momentum from the oars was applied.
This concept, apart from the oars, is very similar to how a submarine's angled/diving plane works today.
5. A French priest made the next big leap towards the modern submarine
In the 1630s, a French priest named Marin Mersenne moved the concept of the submarine one step closer to reality. He suggested that submersible vessels should probably be made of metal, like copper, and be cylindrical in shape with tapered ends.
This, he argued, would be the only way to ensure such ships could withstand the pressures at depth. His suggestion proved to be quite influential, as most submarine designs would later adopt a porpoise-like shape (and were constructed of metal).
6. The "Rotterdam Boat" was another important submarine historical milestone
Proving Leonardo da Vinci correct, it was not long before militaries around the world realized the weapon's potential for submersible vehicles. During the First Anglo-Dutch War (1652 to 1654), a man named Louis de Don built a vessel called the "Rotterdam Boat."
This semi-submersible vessel was effectively a large underwater battering ram, designed to punch a hole in the hull of an enemy ship without being seen.
While the concept appeared sound on paper, the vessel proved ineffective in combat, as it was unable to move once launched.
7. The first true proto-submarine was developed by the French
After these leaps forward in thinking about submarines, it would be the 1800s before the first true submarine prototypes were developed. One of the first came from the French navy in the form of the 1863 Le Plonguer ("The Diver").
Powered by compressed air engines, this was one of the first submarines that did not rely on human-powered propulsion.
8. The Americans made the next advances in submarine technology
Another major milestone in the history of submarines came from the New World. First, during the American War of Independence and the later American Civil War, major breakthroughs occurred in submarine technology.
One of the first submarines to alter its buoyancy by pumping water in an out of its skin was David Bushnell's "Turtle," which was developed in 1775, during the American War of Independence. This was a one-man, hand-crank, propeller-powered vessel that became the first to be used in combat.
The "Turtle," piloted by Ezra Lee, attempted to sink HMS Eagle as she was anchored at New York Harbor in 1776, although the attack failed.
Skipping forward a few years, the first submarine to sink an enemy vessel came during the American Civil War.
With Union forces successfully blockading southern ports, the Confederate navy sought other means to alter the balance of power. They developed another early submarine called the H.L. Hunley.
This oar-propelled submersible attacked and sunk the USS Housatonic with an explosive attached to the end of a spar at the vessel's nose. Both the Union and Confederate vessels were lost.
9. John Philip Holland developed the first true modern submarine
Probably the most important milestone in submarine history was the work of the Irish-American inventor John Philip Holland. Known as the "Father of the Modern Submarine," Holland's submarine would be first to be accepted by the United States Navy.
A staunch Irish separatist in his youth, Holland developed a vessel called the "Fenian Ram." This was a small submarine designed to attack and sink British Royal Navy ships.
Holland and his financial backers, The Fenian Society, would soon fall out, and Holland would find other buyers for his work.
Building on the lessons learned from the "Fenian Ram," Holland and his company eventually developed the first truly practical submarine, called the "Holland" series.
These were to prove incredibly successful, and orders came in from various navies around the world including the United States and, ironically, the Royal Navy.
The modern submarine was born. War at sea would never be the same again.