The Tribal or F class was a class of destroyers built for the Royal Navy. Twelve ships were built between 1905 and 1908 and all saw service during World War I, where they saw action in the North Sea and English Channel as part of the 6th Flotilla and Dover Patrols. Design The preceding River- or E-class destroyers of 1903 had made on the provided by triple expansion steam engines and coal-fired boilers, although was powered by steam turbines. In November 1904, the First Sea Lord "Jackie" Fisher proposed that the next class of destroyers should make at least and should use oil-fired boilers and steam turbines as a means of achieving this. This resulted in a larger ship to provide the required doubling of installed power over their predecessors, but also pushed the design to the limits of capability of contemporary technology. As a result, the Tribals were severely compromised and a somewhat retrograde step after the successful River class; they were lightly built and proved to be fragile in service. More alarmingly however, they were only provided with 90 tons of bunkerage, and with high fuel consumption resulting from a high power output of , they were highly uneconomical and had a severely limited radius of action; Afridi and Amazon once used 9.5 tons of oil each simply to raise steam for a three-mile (5 km) return journey to a fuel depot. Design details were left to the individual builders, as was Royal Navy practice at the time for destroyers. As a result, no two were alike and there was considerable heterogeneity of detail and appearance, Most noticeably the number of funnels varied from three, in Cossack and Ghurka, to six in Viking; the latter, with two single and two pairs of funnels becoming the only six-funneled destroyer ever built. With a light mainmast aft, they were the first British destroyers to have two masts. The first five ships were designed with the armament of three QF 12-pounder guns, an improvement from the single 12-pounder and five 6-pounder guns that the River class was completed with, while the number of torpedoes remained at two tubes. From the sixth ship (Saracen) onwards, however, the armament was again increased, to a pair of BL guns, with one gun mounted forward and another on the quarterdeck. From October 1908, the first five ships were modified by adding another pair of 12