Our First Line of Defence—The Great Change of Front—Close Blockade and an Oversea Base—The New War-Plans: Distant Blockade—Manœuvre Experiments, 1912 and 1913—Prowling Squadrons—The Perils of Surprise—The Limits of Precaution—A Bolt from the Blue—Cordons—The Limits of German Morality—The Invasion Problem and the Expeditionary Force—The Invasion Committee—First Lord’s Notes—The South and East Fronts Compared—Raid or Invasion—Impossibility of Close Blockade—The Patrol Flotillas—The Coastal Watch—A Bolt from the Grey—Possible German Objectives for Raids—Assumptions and Conclusions—Difficulties of Preparation—The Initial Dangers the Greatest—Letter to a Friend—The Other Side. The traditional war policy of the Admiralty grew up during the prolonged wars and antagonisms with France. It consisted in establishing immediately upon the outbreak of war a close blockade of the enemy’s ports and naval bases by means of flotillas of strong small craft supported by cruisers with superior battle fleets in reserve. The experience of 200 years had led all naval strategists to agree on this fundamental principle, ‘Our first line of defence is the enemy’s ports.’ When the torpedo was invented, the French tried to frustrate this well-known British policy by building large numbers of torpedo-boats, and the Admiralty, after some years, retorted by building torpedo-boat destroyers. These destroyers fulfilled two conditions: first, they were large enough to keep the seas in most weathers and to operate across the Channel for sufficient periods; secondly, their guns were heavy enough to destroy or dominate the French torpedo-boats. Thus, in spite of the advent of the torpedo, we preserved our power to maintain stronger flotillas in close proximity to the enemy’s naval bases. Meanwhile, all along the South Coast of England a series of fortified torpedo-proof harbours in the neighbourhood of our great naval establishments afforded safe, close, and convenient stations for our battle fleets and other supporting vessels when not actually at sea. When early in the present century our potential enemy for the first time became not France, but Germany, our naval strategic front shifted from the South to the East Coast and from the Channel to the North Sea. But although the enemy, the front, and the theatre had changed, the sound principle of British naval strategy still held good. Our first line of defence was considered to be the enemy’s ports. The Admiralty policy was still a close blockade of those ports by means of stronger flotillas properly supported by cruisers and ultimately by the battle fleets.