S-day

M day, M Day and M-day redirect here. For the Marvel Universe event, see Decimation (comics) The military designation of days and hours within the North Atlantic Treaty Organisation (NATO), is specified in AAP-6 (STANAG 3680), NATO Glossary of Terms and Definitions, and marked (NATO) in what follows. Those entries marked (US) are specific to the U.S., and defined only in Joint Publication JP 1-02, Department of Defense Dictionary of Military and Associated Terms.
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Operation Sealion (Unternehmen Seelöwe in German) was a World War II Nazi German plan to invade the United Kingdom, beginning in 1940. The operation was abandoned in September 1940.
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