Defence and Communications Branch. The wing was formed in response to the murder of three officers. The Commissioner requested applications from officers within the service who had experience in the handling of firearms, such as ex-members of the armed forces or those who attended shooting clubs. The officers who applied were sent to the Small Arms Wing of the School of Infantry to become permanent instructors for the service's newly formed firearms wing. Upon the officers' return to the service, they trained firearms officers. After the unit had changed its name from D6 to D11, the Instructors possessed a limited operational role that consisted of providing CS gas at sieges. This progressed to providing tactical advice and support and in 1975 as a direct result of the Munich Olympic games massacre, D11 was formally given an operational role in Counter Terrorist and serious armed crime operations. Its officers qualified using the Smith & Wesson Model 28 or Model 19 .357 revolvers, Browning Hi-Power semi-automatic pistols, the Heckler & Koch MP5 SD (Suppressed) submachine gun and the Remington 870 shotgun with some officers being trained and authorised to use the Enfield Enforcer 7.62 mm sniper rifle and Heckler & Koch 93 semi-automatic rifle in 5.56mm for counter-sniper roles. Throughout the 1970s, the branch increased in size, with additional firearms instructors being recruited to meet the increase in the demand for firearms training. During the 1970s, D11 officers qualified their students in the Smith & Wesson Model 36 and the Model 10 revolvers. In response to operational demands, the department underwent restructuring in 1987 becoming PT17 (Personnel & Training) and the introduction of non-instructors who formed level 2 teams. Their role was to deal with pre-planned and response operations not involving hostages or suspects with 'exceptional firepower'. These tasks remained the responsibility of the teams of Instructors who became Level 1 teams. In 1991 following the shooting and stabbing of several police officers, the Armed Response Vehicles (ARV's) were introduced and put under the control of the unit drastically increasing its manpower and necessitating its move to Specialist Operations and a new designation of SO19, the Force Firearms Unit. The unit maintained its training role and continued to train the Met's 4,800 officers who were redesignated as Authorised Firearms Officers (AFO). The level 2 officers underwent enhanced training and those that passed joined selected Level 1 instructors to become SFO's (Specialist Firearms