The submarine was rejected after operational trials by European governments in the early 19th century.
These included French, British and American naval authorities.
Nevertheless, at the turn of the 20th century, numerous countries had included submarines in their naval fleets, albeit on a rather small level.
Those boasting submarines included Russia, Japan, Greece, Britain, France and others. Germany by no means had the largest number of them.
Find more content related to the sinking of RMS Lusitania in our special report
One of the most significant events in instructing nations of the destructive value of the submarine came about on September 22, 1914.
While on patrol, the German submarine, U9, attacked and sank three ageing British cruisers.
These were the HMS Aboukir, HMS Cressy and HMS Hogue.
All had been patrolling together in the North Sea when they were spotted by Capt. Otto Weddingen, who was in command of the U-boat.
In just 45 minutes, all three vessels were torpedoed and sank with the loss of 1,400 men.
Only 837 survived the attack. The submarine crew were hailed in Germany as heroes, while British Admirals faced much criticism at home.
Initially, it had been claimed that the ships were sunk by mines; however, the lethal capacity of the submarine had been clearly demonstrated that day.
This particular action — exposing the vulnerability of naval ships when targeted by submarines — may have played a part in the Lusitania story.
It may even have contributed to an increase in the number of those lost on RMS Lusitania. A royal naval cruiser was directed to flee from the scene of the sinking Lusitania and ordered to return back to Queenstown.
HMS Juno was an ‘Eclipse’ class light cruiser that had been built and launched in 1897.
In August of 1914, already deemed to be an old ship, she was assigned as a constituent part of Cruiser Force E, also known as the 11th Cruiser Squadron, with four other, similar vintage cruisers, patrolling the southern entrance of, and approaches to, the Irish Sea.
The squadron, under the command of Rear Admiral Phipps Hornby, comprised of HMS Juno, HMS Minerva, HMS Doris, HMS Venus, and HMS Isis.
Their area of operation — at least at the beginning of the war — extended out westwards beyond the Fastnet lighthouse, on the Atlantic shipping routes that approach Ireland.
Their remit included the patrolling of this area to ‘cover liners, cargo carriers and tramp steamers approaching the British Isles from the Atlantic’.
Despite the fact that these ships were on the front line of protecting merchant shipping, the information they received was often at least 24 hours old.
In the much-criticised handling of Admiralty intelligence, solid information on the activities and the movements of submarines, in and near the western approaches, was often not conveyed to the very ships charged with protecting merchant travellers.
The Admiralty’s fear of having HMS Juno sunk by a submarine may have outweighed the humanitarian consideration of saving civilians on the day that RMS Lusitania was torpedoed.
Rather than pick up passengers from the stricken ship and/or engage with the enemy, a warship of the Royal Navy was to turn its back on both and flee to the safety of Queenstown.
While the maelstrom of death and destruction was unfolding around the Lusitania and its passengers, another scenario was being played out that leaves questions as yet unanswered to this day.
The movements of HMS Juno probably led to one of the early Lusitania conspiracy theories. Official explanations, such as they are, still leave uncomfortable questions.
The five Cruiser Force E ships were stationed in and around the southern approaches to the Irish Sea.
Since February 19, 1915, this area was included in the German designated ‘war zone’ that had been announced by the German government on February 4.
These ships, despite their age, were warships. They had been designed and built with conflict in mind. They were crewed by Royal Naval personnel; they were armed with heavy, six-inch guns.
One must assume they were in position as a deterrent to submarine attacks. That they were there as protection to the merchant ships using the busy lanes to Liverpool, and to other ports on the East coast of Great Britain.
They were there to keep the access open to the Irish Sea. Given the type of ship, and their duty while stationed there, one would expect they were equipped to deal with the threat of submarine attack.
And that they were better equipped than an unarmed merchant ship to damage and/or sink a submarine, if that should become necessary. Unless they were deployed for leisure, one must assume that they were there to engage with the enemy, if that situation should arise.
Why, then, was RMS Juno instructed to flee a danger zone when it arose? On the morning of May 7, 1915, when RMS Lusitania had entered the ‘war zone’, HMS Juno was operational off the south coast.
From midnight up until 2pm that day, she was steaming in an east-to-west direction along the coast.
Captain Turner, aboard RMS Lusitania, may have been expecting a naval escort through the zone from a navy ship and never got it.