They were able to keep the Channel clear of submarines long enough to permit the passage of the troops, which England from time to time during the first year of the war sent to the Continent, and permitted the participation of the troops of the British overseas dominions, the troops from Canada joining those in France, and the troops from New Zealand and Australia taking their places in the trenches along the Suez Canal and on the Gallipoli Peninsula. Thus, to a certain extent, the advantage of continuous railroad communication which was enjoyed by the Teutonic allies "inside" the arena of military operations was offset by the naval communication maintained by the Entente Powers "outside" the arena of military operations. CHAPTER XXXIII FIGHTS OF THE SUBMARINES When, on the 5th of February, 1915, the German admiralty proclaimed a "war zone" around the British Isles and announced that it would fight the sea power of the Allies with submarines, a new era in naval warfare had opened. In all previous wars, and in the earlier months of the Great War, submarines were employed as auxiliaries to the larger naval units. The Germans were the first to use them as separate units. The idea of sending a fleet of submarines out on to the high seas was a new one, and had been impossible in the last war in which they had been used--that between Russia and Japan. But the improvements which had been made in their design and equipment since then had made an actual cruising submarine possible, and made possible the new phase of naval warfare inaugurated by the German admiralty. While Germany was the last great sea power to adopt the submarine as a weapon, both England and Germany, in the years immediately preceding the war, had spent the same amounts of money on this sort of craft--about $18,000,000--but while the Germans had later given as much attention to them as to any other sort of naval craft, the British authorities did not figure on employing the submarine as a separate offensive tactical unit being sufficiently equipped in large ships carrying large guns. And being weaker in capital ships Germany was compelled to rely upon underwater warfare in her campaign of attrition. Not only were the naval authorities of the rest of the world uninformed about the improvements that German submarines carried, but they were fooled even as to the actual number which Germany had built.