Officers). SFO teams replaced the old Level 1 and 2 structure becoming full-time tactical teams dealing with all pre planned armed operations (Robbery ambushes, warrant service and hostage situations etc.) within the Met and providing specialist support to the ARV's. ARV officers provided rapid response to spontaneous firearms incidents, such as armed robberies, being the first such organised system the capital had witnessed. Early ARV officers were issued with Smith & Wesson Model 10s, with others being trained in the use of the Heckler & Koch MP5 semi-automatic carbine. The Model 10 was later replaced by the Glock 17 semi-automatic pistol. Following a further reorganisation in 2005, SO19 became CO19, due to the department's move to the Central Operations Directorate, at the same time the department was renamed from the Force Firearms Unit to Specialist Firearms Command. In January 2012 the branch underwent another name change, becoming SCO19 due to the merger of Central Operations (CO) and Specialist Crime Directorate (SCD) to form Specialist Crime & Operations. Since then SCO19 has again been re-designated as MO19, a result of the 2018–19 restructuring, putting it under Met Ops while maintaining the title of SCO19. While the core function of the branch—to provide firearms training and support—remains unchanged since its creation, its role continually changes to meet the demands placed on it. The branch today fulfills different roles than it did 30 years ago. All aspects of armed policing in the UK are covered by guidance issued by the Association of Chief Police Officers in their Manual of Guidance on the Police Use of Firearms. This manual provides an overview of the basic principles such as rules of engagement and tactics involved in the use of firearms by police officers in different environments along with details of command structures that are in place in all planned and spontaneous firearms operations. Current role Training As of 2007, the Command is responsible for training the 2,594 Authorised Firearms Officers (AFOs) of the Metropolitan Police Service (MPS). These include officers from Protection Command, Counter Terrorism Command, Diplomatic Protection Group, the Aviation Security Operational Command Unit, the Flying Squad (SCD7[5]), Specialist and Royalty Protection Command and the armed officers from MO19 itself. Potential AFOs are invited to attend the Training Centre after they have undergone the written tests and interviews, and successfully completed their probationary period with a further two years in a core policing role.