"It is not widely appreciated that mines were by far the most effective weapon deployed by German against the Royal Navy in WWI. They cost Britain five battleships, three cruisers, twenty-two destroyers, four submarines and a host of other vessels. Mines were generally combated by a civilian force that sailed in a variety of commandeered vessels such as fishing boats and paddle steamers. This unlikely armada saved the day for Britain and her allies. After 1916 submarine attacks on merchant ships became an even more serious threat to Allied communications, but enemy submarines were far less damaging to British warships than mines. Whereas in 1914 the Admiralty rather scoffed at mine laying as a sneaky un-British form of sea warfare, by the later stage of the war the Royal Navy learnt to use mines as a primary anti U boat weapon, developing an amazing variety of mined obstacles and mine laying vessels."

On 26 October 1914 the Second Battle Squadron of the Royal Navy (2BS) put to sea for exercises, They were to fire their main armament at targets towed by two tugs. They were escorted by the light cruiser Liverpool. They were all 'super dreadnought’ battleships with names redolent of the great days of the Royal Navy: King George V, Audacious, Centurion, Monarch and Thunderer. The commander of this formidable squadron was Vice Admiral Sir George Warrender Bt KCB. Warrender was in every respect typical of the admirals of the Royal Navy of the time; he was strong and he was well-respected by his officers. Unfortunately, he was not able to see threats in the reality of contemporary military living in the twentieth century. One who understood and took these new threats seriously was Admiral Sir John Jellicoe.

Jellicoe was clear to point out to his superiors that a new type of naval tactics and naval war was coming. His answer to this were mines and minefields around harbors and important strategic elements within and outside the British sovereignty. The battleship Audacious became an early victim in what would now be a large and visible change of the sea with the use of sea mines. Initially feared that she had been hit by a torpedo, but it was not a submarine which had caused damage to Audacious , it was the Berlin (liner, 17.000 tons), a fast, armed merchant cruiser with 200 deadly mines. In this story the battleship Audacious an example of how vulnerable large naval vessels were. She sank later by a relatively small mine of guncotton (nitrogen), only 160 lb.

Many other ships survived such a blast, where the output of more than 500 lb of explosive  were typical. This indicated how the British naval vessels were structured under the surface. After the loss of Audacious, naval operations could not ignore danger of mines. Throughout the war, 1914-1918, mines caused far more damage than guns and torpedoes. The Hidden Threat illustrates how the Royal Navy handled this situation, through the use of technology to defend itself both defensively and how to take advantage of this offensive against the enemy. The book shows many different scenarios; both the British and the Germans used mines in their military operations. Many different types of mines are detailed, such as magnetic and contact mines. Somewhere around 600 -700 ships were engaged over the course of the war to remove hundreds of thousands of mines that had been laid. The book is well documented and contains interesting photographs of the minefields at sea, as well as images of ships and mine laying and submarines. I see the book as an excellent reference material and experience blended with real facts and history.