History of Orkney should continue to be observed in Orkney and Shetland. Thus the udal succession and mode of land tenure (that is, absolute freehold as distinguished from feudal tenure) lingered to some extent, and the remaining udallers held their lands and passed them on without written title. The islands cluster round the huge deep-water anchorage of Scapa Flow like a protecting hand, and in both World War I and World War II, the Royal Navy had a major base there, enabling them to challenge any attempt by German warships to emerge into the ocean through the Norwegian Sea. After the Armistice in
Naval warfare of World War I came under Bulgarian control in 1916 as "Podvodnik No. 18". Russian mines sank one Bulgarian torpedo boat and damaged one more during the war. In the Baltic Sea, Germany and Russia were the main combatants, with a number of British submarines sailing through the Kattegat to assist the Russians. With the German fleet larger and more modern (many High Seas Fleet ships could easily be deployed to the Baltic when the North Sea was quiet), the Russians played a mainly defensive role, at most attacking convoys between Germany and Sweden. A major coup for the Allied forces occurred on August