The military faction that takes Rick Grimes is known by the acronym CRM, meaning Civic Republic Military. The CRM is the armed force of the Civic Republic, a secretive post-apocalyptic government centered in Philadelphia.
Rick is taken by helicopter after the bridge explosion in the Season 9 episode “What Comes After.” Jadis, also known as Anne, contacts the helicopter group and identifies Rick as an “A,” after which he is transported away from his friends and presumed dead for years. Later stories reveal that the CRM has held Rick as a consignee and attempted to recruit him into its military structure.
The CRM initially presents itself as a force protecting the remnants of civilization, but its leadership uses extreme secrecy and violence to preserve the Civic Republic. Its operations include the destruction of survivor communities considered threats, including Omaha and the Campus Colony. In The Walking Dead: The Ones Who Live, Rick and Michonne expose the organization’s crimes, leading to the military’s reform under civilian oversight. CRM is not a generic intelligence-agency acronym in this universe; it specifically refers to the Civic Republic Military.