After the Action of 19 August 1916, in which the Grand Fleet had lost two light cruisers to German U-boat attacks, Admiral John Jellicoe, the fleet commander, decided that the fleet should not be risked in such sorties unless the High Seas Fleet ventured north or the strategic situation warranted the risk. For its part, the German fleet remained in port or trained in the Baltic Sea through 1917, as both sides had largely abandoned the idea of a decisive surface battle in the North Sea. Both sides turned to positional warfare, laying fields of naval mines, and Germany resumed the unrestricted submarine warfare campaign early in the year. As a result, "Revenge" and the rest of the Grand Fleet saw no action during the last two years of the war.