The worsening security situation in south County Armagh , especially after the killing of three British soldiers at an observation post in November 1975 and the massacre of ten Protestant workers in January 1976 , prompted British PM Harold Wilson to publicly acknowledge the presence of D squadron of the Special Air Service ( SAS ) , which was deployed to Bessbrook Mill . The ambush of the observation post exposed the fact that conventional military tactics had n't worked for the British Government in South Armagh , since the British Army report of this incident identified a number of basic mistakes regarding camouflage , routine patterns and the observation post 's arrangement
massacre of ten Protestant workers
Kingsmill massacre
Flagstaff hill incident