Operation Green (German: Unternehmen Grün) often also referred to as Case Green (Fall Grün) or Plan Green (Plan Grün), was a full-scale operations plan for a Nazi German invasion of Ireland in support of Operation Sea Lion (Unternehmen Seelöwe), the invasion of the United Kingdom, during World War II.[1][2] Despite its detailed nature, Operation Green is thought to have been designed only as a credible threat, a feint, not an actual operation. Plan W, a planned occupation of all of the Free State by the British Armed Forces, was drafted by the British military in secret liaison with the Irish government to counteract any German invasion.