While the German High Seas Fleet was bottled up in the Baltic Sea and the Norwegian Fjords by the British Home Fleet, their Schnellbootes operated in the English Channel almost with impunity. The "E-Boats" so named by the British were fast and powerful. Triple shafted driven propellers by powerful diesel super-charged engines, 21 inch torpedoes and 20mm and 37mm canons combined with speeds in excess of 40 knots, made them a powerful convoy interdiction weapon in the English Channel. They outclassed the smaller British M.T,Bs and not until the Allies had mastery of air in the latter half of the war and had developed their own answer to the E-Boat; the Fairmile Marine D model "Dog Boat" did the Allies come to grips with them. The E-Boats operated from bases in the Fjords of Norway to the German occupied island of Gurnsey, inflicting crippling losses on English coastal shipping.