For centuries, militarists recognized that a submarine’s invisibility provided it with two distinct advantages: surprise in the attack and the ability to withdraw with impunity. From earliest recorded times, inventors attempted to build combatant submarines. They mastered watertightness and ballasting but could not devise a practical means for propelling the submerged submarine in a controlled direction in the face of tides and currents.
The development of an efficient coal-fired steam engine in the 1800s offered a possible solution to submerged propulsion. Steam could be “stored” under pressure for a limited time. Inventors designed submarines that were to travel on the surface to the combat zone powered by steam engines, then submerge for the attack and withdrawal, powered by stored steam. But steam-powered submarines proved to be less than satisfactory. The engines generated nearly unbearable heat inside the small hulls. The furnaces emitted sooty exhaust that could be seen for miles at sea, robbing the submarine of stealth, one of its chief assets. Moreover, the smokestack had to be disassembled and stored before diving, a cumbersome and time-consuming procedure.
Far better solutions to submerged propulsion became apparent about 1880 with the nearly simultaneous development of the internal combustion engine, the electric motor, and the storage battery. Most inventors designed submarines that were to be powered by gasoline engines on the surface and battery-driven motors while submerged. Others designed submarines powered entirely by battery-driven motors. Still others, combining old and new technology, designed submarines powered by steam engines for surface travel and battery-driven motors for submerged travel. All early versions had drawbacks: Gasoline engines were difficult to start and unreliable in operation, and emitted dangerous fumes. Batteries were bulky, heavy, and weak. Steam engines still generated too much heat.
These propulsion experiments gave promise of a practical submarine. But a breakthrough in weaponry was also needed. The existing weaponry was limited and hazardous: time-fused mines (or bombs), which had to be screwed to the bottom of enemy ships, or spar-mounted contact mines, which had to be rammed against the side of the enemy ship. Both weapons required close—near suicidal—contact with the enemy.
The solution to the weaponry was provided by an English engineer, Robert Whitehead, who lived in Fiume, Austria. In about 1866 he introduced what military historians today would describe as a “stand-off weapon”: an automotive or self-propelled mine or torpedo. The Whitehead torpedo was powered by compressed air stored in a large flask. When released, the air turned pistons, which spun a propeller. The first model was primitive: fourteen feet long and fourteen inches in diameter, weighing about 300 pounds. It had a range of 700 yards at 6 knots. The experimental “warhead” in the nose, which was set off by a contact “pistol” when it hit the side of a ship, was puny: eighteen pounds of dynamite. But it worked.
The Whitehead torpedo did not create an immediate sensation in naval circles. But Whitehead soon increased its size, power, range, and the lethality of the warhead. An Austrian, Ludwig Obry, adapted the gyroscope to the torpedo, giving it directional control. With each improvement, naval authorities paid greater interest. Before long the idea took root that Whitehead torpedoes, fired from cheap, small, speedy vessels, might be employed effectively to attack expensive big ships of the line. In due course this concept evolved into the torpedo boat, then into the torpedo-firing destroyer, which were embraced first by weaker naval powers and ultimately by all navies.
The Whitehead torpedo had not been envisioned as a submarine weapon, but by happenstance it was just what submarine proponents had been looking for. With its ability to sneak up on the quarry submerged, unseen and undetected, shoot, then retire submerged with relative impunity, the submarine could be a superior torpedo launcher to the torpedo boat or destroyer.
Soon all submarine designers were recasting plans to incorporate the Whitehead torpedo. This breakthrough stimulated considerable interest among the weaker naval powers, but introduced new levels of complexity. The weapon system required a torpedo tube in the bow of the submarine’s pressure hull and a compressed air system for “charging” the torpedo and for booting it from the tube. The tube had to have interlocking inner and outer doors that could be flooded for firing and drained for reloading a second or third projectile. Since the latest torpedoes were very heavy—and getting heavier as the warhead increased in size and lethality—a compensating ballast system had to be devised to offset the sudden loss of weight upon firing and the shifting about of reloads. Otherwise the delicately balanced submarine would go out of control, popping to the surface or plunging to the bottom.
Submarines employed compressed air for blowing main ballast tanks and for other purposes, stored in steel bottles under very high pressure. The incorporation of gasoline and steam engines and battery-powered motors provided the submarine with a power source to operate onboard air compressors. Hence submariners had the equipment and know-how for providing the considerable compressed air required for charging the torpedo flasks and for ejecting the torpedo from the tube.
These technological breakthroughs launched a submarine arms race. By 1890 torpedo-firing submarines utilizing a variety of propulsion systems (all steam; all electric; steam-electric; gas-electric) were under construction worldwide. The stronger naval powers—Great Britain, Germany, the United States—showed little interest in the submarine, but the weaker naval powers—France, Russia, others—embraced it with a passion. Unwilling to compete in the Anglo-German naval race, France became the first nation in the world to place substantial state resources behind submarine development. By 1906 the French navy had nearly ninety submarines in commission or under construction.
Of the submarine designers, an Irish immigrant to the United States, John P. Holland, was the most inventive and able. His boat, Holland, equipped to fire the Whitehead torpedo, was the engineering marvel of the 1890s, superior to all submarines in the world. For surface operations she employed a four-cylinder, 160-horsepower gasoline engine, which gave her a cruising speed of 7½ knots. For submerged cruising she had a sixty-cell battery, supplying electrical power to a 70-horsepower motor, which gave her a top speed of about 6½ knots for about three hours and twice that endurance at slower speed. The propulsion system was versatile and flexible. The gasoline engine could be used for surface propulsion, for turning a generator to charge batteries, or for operating the air compressor. The electric motor could be used for either surface or submerged propulsion or for starting the balky gasoline engine. The battery also supplied power for the many smaller motors throughout the boat (periscope hoist, bilge pump, trim, tank pumps, etc.) and for internal lighting.
Holland founded the Electric Boat Company in New London, Connecticut, and sold submarines to any and all comers. The U.S. Navy was his first customer. In 1900 it bought the prototype Holland and christened it U.S.S. Holland (Submarine Number 1). After rigid trials, the navy bought six more Hollands for “coastal defense purposes” and later, a dozen more improved models. Alarmed by France’s large—and swelling—submarine force, Great Britain’s Royal Navy bought five Hollands in 1901 for evaluation purposes. Astonished by the efficient performance of these little craft, the British embarked on a substantial submarine buildup in 1905. That same year Holland sold submarines to the belligerents Russia and Japan, producing the seeds for the submarine forces of both those nations.
The gas-electric boat was superior to all others, but it was dangerous. Notwithstanding all efforts to prevent it, gasoline seeped into bilges, emitting explosive fumes. Deadly carbon monoxide leaked from the exhaust pipes. Several gas-electric boats in the United States and British navies blew up; some crewmen were killed bv exhaust fumes. These continuing dangers led submarine designers to explore two less volatile and toxic internal combustion fuels: paraffin (akin to kerosene) and “heavy” or “diesel” oil, named for the German inventor Rudolph Diesel, who in 1895 had demonstrated the first “heavy oil” or, as it came to be known, diesel engine.
Engineers in Germany slowly brought the paraffin and diesel engines forward. Owing to the difficulty of producing a reliable diesel engine that was compact and light enough to fit inside a submarine hull, the paraffin engine led by several years. The German arms conglomerate, Krupp A.G., was first to build a paraffin submarine—a tiny prototype, christened Forelle (Trout), which was launched in 1902. German industry was then in good position to exploit submarine technology but it made little headway. The reason was the unyielding opposition of Grand Admiral Alfred von Tirpitz, State Secretary of the Navy. He had persuaded Kaiser Wilhelm II to embark on a massive big-ship building program, designed to outgun the big but aging Royal Navy. Singlemindedly pursuing this ambitious undertaking, von Tirpitz refused funds for unrelated, experimental, unproven weapons and discouraged all discussions of “cheap” alternatives to his big-ship navy, such as submarines.
Sensing a new and profitable market, the Krupp firm pursued the submarine in spite of von Tirpitz’s indifference. In 1904 Krupp sold the Russians the paraffin Forelle and then obtained orders for three larger paraffin boats, known as the Karp class. In subsequent years it negotiated sales agreements with numerous nations (Italy, Austria-Hungary, Norway) for larger, more sophisticated paraffin boats. At the same time Krupp mounted intense pressure on German engineers to bring the diesel engine to a practical stage for submarines.
Although the staff of the German Imperial Navy concurred with von Tirpitz’s big-ship program, it fretted about the submarine arms race, which was being fueled in part by German industry. It seemed imprudent to export this important military technology, which, in the wrong hands, could cause the big-ship Imperial Navy immense grief. At the least, the staff argued, the Imperial Navy should acquire a submarine for evaluation. Yielding to these pressures, von Tirpitz finally authorized Krupp to build one submarine, or Unterseeboot (abbreviated as U-boot, or in English, U-boat). What emerged was a slightly larger and improved copy of the paraffin-powered Karp class, designated U-1. Upon her commissioning in December 1906, it was noted that Germany was not the first but rather the last major naval power to adopt submarines, and these were indebted to American technology.
Having introduced the paraffin engine and other innovations, including superb periscope optics, Krupp submarine engineers were determined to further outdo submarines of competing naval powers. Over the next several years they proposed ever larger, longer-ranged, faster, better-armed models. Still not fully persuaded that the submarine had a place in the Imperial Navy, von Tirpitz only grudgingly released funds for new construction, and in their efforts to move ahead quickly, the engineers encountered many technical setbacks. As a result, the embryonic German submarine force grew, haltingly.
The German designers, meanwhile, had been pressing ahead with grander ideas. The ambitious goal was to produce, in a single, catch-up leap, a reliable oceangoing paraffin boat about 185 feet long and with a displacement of about 500 tons. It was to be armed with four torpedo tubes (two forward, two aft), with storage space for one reload in each torpedo compartment. The designers succeeded, producing several such submarines. In the years 1908 to 1910 the Imperial Navy ordered fourteen big paraffin boats, the nucleus of the emerging German submarine force. The paraffin engine was safer than gasoline and more efficient than steam, but it had one enormous military drawback: It emitted dense white exhaust, which was visible for miles at sea. For that reason submarine designers anxiously awaited a reliable diesel engine. But it came on very slowly. The French—not the Germans—were first to fit a diesel engine in a submarine. Then the Russians. The British were next. Other nations, including Italy and the United States, turned to this new technology, but German designers, demanding higher performance and reliability, held off. However, in 1910 Germany finally curtailed construction of paraffin boats and shifted to diesel, the last major power to do so. In the period 1910-1912 the Imperial Navy ordered twenty-three diesel-electric boats.
By the summer of 1914, on the eve of World War I, the submarine arms race, scarcely a dozen years old, had produced an astounding number of boats worldwide: about 400. Many of these were “old technology” gasoline- or steam-propelled submarines of limited or no military value, but a fourth of the boats were modern oceangoing diesel-electrics, armed with four or five torpedo tubes. Great Britain—not Germany—had the largest submarine fleet: seventy-six, with another twenty on the building ways. France ranked second, with seventy boats (many steam-electric) and twenty-three under construction. Czarist Russia came third with forty-one boats, most of them obsolescent. The United States ranked fourth with thirty-one, and eight more under construction. Germany held fifth place with twenty-six commissioned boats and fifteen under construction.
Undefined as yet was the role submarines were to play in war. Originally conceived as small, short-legged “coast” and “harbor” defensive weapons to thwart or counter enemy raids and blockades, they had grown into offensive oceangoing craft with substantial durability and firepower. They were believed to be capable of waging war against enemy battle fleets, acting alone or as part of a group. They were also capable of hit-and-run attacks on an enemy’s maritime commerce in a guerre de course. Mounted systematically and with great intensity, a submarine guerre de course could produce a new kind of blockade, to which the “island” nation of Great Britain would be peculiarly vulnerable.
However, a submarine guerre de course, or war on commerce, would impose numerous legal, moral, and practical difficulties. Over the centuries civilized nations had evolved rules and regulations known as “prize laws” with respect to commerce raiding and had pledged in various international treaties to abide strictly by them. No merchant vessel of any kind was to be sunk at first sight without warning. Specific procedures were to be followed. The interceptor was required first to stop the merchant ship by signal or, if necessary, “a shot across the bow.” The interceptor was then required to establish by a ritualized procedure (known as “visit and search”) whether the accosted ship was friend, foe, or neutral. If found to be a friend or a neutral transporting innocent or innocuous cargo, the ship was allowed to proceed unmolested. If found to be a foe, or a foe disguised as a neutral, or a neutral transporting “contraband” (i.e., war matériel or other prohibited cargo) to the enemy, the interceptor was permitted to capture (or sink) a foe and to capture an offending neutral. A captured ship was to be manned by a “prize crew” and sailed to a friendly or neutral port and turned over to a legal tribunal. Judges would then decide whether or not the capture had been legally correct and if the neutral’s cargo was indeed contraband. If the tribunal condemned the neutral for transporting contraband, both ship and cargo could be sold at auction and the proceeds distributed to the interceptor or its sponsoring government. If, on the contrary, the tribunal found the interceptor to have incorrectly interpreted the cargo as contraband, the interceptor and/or its sponsoring government was subject to fines and damages.*
Beyond that there had evolved a strict, humane code of the sea with respect to the crews of merchant vessels. In various international treaties† it had been agreed that merchant ship crews—and passengers—were “noncombatants” and were not to be harmed or abandoned. If the interceptor found it necessary to sink the merchant vessel for whatever reason, it was required to take aboard the crewmen and passengers and land them ashore or to place them (and the ship’s papers) in sound lifeboats, well supplied with provisions, sails, and navigational equipment, and give them specific directions and courses to the nearest land, or, if known, the nearest neutral ship thereabouts. Any violation of this code would be considered inhumane and barbarous and subject to severe punishment.
Submarines waging a guerre de course could not conveniently or safely abide by all these complicated rules. To do so would surrender the submarine’s greatest asset: surprise in the attack. Stopping a ship by signal or a shot across the bow on the high seas for the ritualized “visit and search” would be an extremely difficult undertaking. The submarine would have to come to the surface, where it was most vulnerable. Many merchant ships could simply bend on more steam and outrun even the most modern submarines, which could make only 12 to 15 knots. A bold merchant ship captain might even attempt to ram the submarine.
Assuming the ship did stop on signal, the “visit and search” ritual presented other difficulties. Submarines did not carry enough manpower or small boats to board a merchant ship for a proper inspection. A small boarding party that went over on a rubber raft could be captured and held hostage, leaving the submarine captain to face the unwelcome choice of letting the ship (and his captured men) proceed or torpedoing it with the probable loss of his men. Should these difficulties be surmounted and the ship found to be a neutral with a contraband cargo, with the limited manpower available, it would be exceedingly difficult to capture the ship, man it with a “prize crew,” and sail it to a friendly or neutral port for legal adjudication. If the ship was to be sunk for whatever reason, the submarine could not take the crew aboard and land it ashore or otherwise provide much meaningful assistance. It would be necessary for the submarine to wait for the crew to provision its lifeboats, abandon ship, and stand well clear of torpedoes or gunfire, a tedious, high-risk process that would expose the submarine to constant danger of sudden counterattack from enemy naval forces.
These considerations were much discussed behind closed doors in naval establishments and in professional journals. Some navalists, including Britain’s foremost submarine advocate John (Jacky) Fisher, concluded that if submarines engaged in a guerre de course, the prize laws could in no way be adhered to. “However inhuman and barbarous it may appear,” Fisher wrote in a prescient, prewar paper, “there is nothing else the submarine can do except sink her captives.” In response, Winston S. Churchill, First Lord of the Admiralty* in 1911, spoke for many British naval officers: “I do not believe this would ever be done by a civilized Power.” Hence on the eve of World War I, the gentlemanly and naive assumption that submarines would only attack enemy warships was the prevailing view.