The RAF were to fly three Hurricane fighter squadrons into Baldonnel Airfield southwest of Dublin and two Fairey Battle light bomber squadrons into Collinstown to attack German troops in Cork. The British 1st Heavy Anti-Aircraft Regiment was to be moved into the State to defend the Drogheda viaduct, Collinstown, and Baldonnel. The Royal Navy was to issue instructions that all British and foreign ships depart from Irish ports. Vessels in Londonderry were to head for the Clyde and boats in Belfast were to head for Holyhead and Liverpool. As many ships as possible would be cleared from Irish ports and taken to the Clyde, Holyhead and Fishguard. Royal Navy officers in Dublin were to direct this exodus and the taking on of refugees was not to be encouraged. British submarines were to patrol off Cork and the Shannon in readiness for an invasion, and should one occur, the Royal Navy was to declare a "sink on sight" zone in the western approaches and off the south and west coasts of Ireland.