It was no small part in the naval war in the North Sea that was played by the light cruisers and destroyers of the Harwich Force and the Harwich Submarine Flotilla. Their province it was to haunt the enemy's coasts for four years in all seasons and weathers, and harass the Hun in his own waters. It is a story of daring strategy, ingenious devices, constant stubborn attack, and as stubborn defence. The facts speak for themselves. _Part III_ THE HARWICH AUXILIARY PATROL AND MINE-SWEEPING FORCE CHAPTER XI THE ROYAL NAVAL TRAWLER RESERVE CHAPTER XI THE ROYAL NAVAL TRAWLER RESERVE Mine-sweeping trawlers--Captains courageous--Scotch drifters--The motor launches--Keeping open the swept channels. Having in previous chapters dealt with some of the gallant doings in the war of the Harwich Force of light cruisers and destroyers and the Harwich Submarine Flotilla, I will now turn to a third force which had Harwich as its base--the Harwich Auxiliary Patrol and Mine-sweeping Force, whose most valuable and most dangerous work it was throughout the war to clear the sea routes of the enemy's mines over a large and very vulnerable portion of the North Sea, and, incidentally, to attack and destroy the enemy's mine-laying submarines whenever possible, thus keeping open and comparatively safe the channels used by the Harwich Force and those frequented by our merchant shipping. A few years before the war the Admiralty had the foresight to found what may now be regarded as the nucleus of the vast mine-sweeping organisation that has been developed since 1914. When war broke out this nucleus contained a personnel of about a thousand officers and men, belonging to the Royal Naval Trawler Reserve, who used to undergo a short training each year in mine-sweeping, as it was then known; for great indeed has been the progress made since in this by no means simple science. These men were quite apart from the active service ratings of Fleet Sweeping Flotillas. It was realised how utterly inadequate was so small a force for the gigantic task that lay before it, so the Admiralty at once took steps to place the R.N.T.R. on a war footing. Able officers were set to work to organise the undertaking, suitable vessels were acquired, crews were enrolled, and the force expanded rapidly until at last it included approximately 750 sweeping vessels, all manned from the Trawler Reserve, the total of which was 38,000 at the conclusion of the armistice. The magnitude of the work carried out may be gathered from the fact that during hostilities about 2000 square miles of sea were swept daily for mines in our home waters alone, while nearly 10,000 enemy mines were swept up and destroyed.