The Black Ops Division is an original creation only for the "Fullmetal Alchemist (2003 anime)" and does not appear in the original work "Fullmetal Alchemist (manga)".
The Black Ops Division refers to a covert operations group within the military of Amestris. This secretive division is tasked with carrying out covert and often morally dubious missions that are not officially sanctioned or acknowledged by the military hierarchy.
The Black Ops Division engages in various illicit activities, including assassination, espionage, and other undercover operations. These actions are usually kept hidden from the public and even from most of the military personnel, emphasizing their covert nature. In truth, their operations are led by the homunculi in order to instigate wars while maintaining the trust of the Amestrians. Cover stories are fabricated to make it seem like Amestris was not the aggressor.
The Ishvallan war came into being thanks to one of their top secret operations. All of the spec ops soldiers involved were silenced by being taken into lab 5 for human experimentation. In the end, official Amestrian records indicate that the war instead started when a soldier named Juliet Douglas shot an Ishvallan child, concealing the fact that the war was started deliberately.