On 12 October 1940, Hitler issued a directive releasing forces for other fronts. The appearance of preparations for Sea Lion was to be continued to keep political pressure on Britain, and a fresh directive would be issued if it was decided that invasion was to be reconsidered in the spring of 1941. On 12 November 1940, Hitler issued Directive No. 18 demanding further refinement to the invasion plan. On 1 May 1941, fresh invasion orders were issued under the codename "Haifische" (shark), accompanied by additional landings on the southwest and northeast coasts of England codenamed "Harpune Nord" and "Harpune Süd" (harpoon north and south), although commanders of naval stations were informed that these were deception plans. Work continued on the various amphibious warfare developments such as purpose-built landing craft, which were later employed in operations in the Baltic.