#espionage

• Abwehr — The military intelligence and counterintelligence service of the German armed forces (Reichswehr and later Wehrmacht), operating under the High Command between 1920 and 1944. Initially created with a strictly defensive role to bypass the restrictions of the Treaty of Versailles, the service expanded under Admiral Wilhelm Canaris into a complex network of foreign espionage and sabotage, while also serving as a hidden core of internal resistance against the Nazi regime until its dissolution by Hitler.
• Intelligence network — The totality of secret agents, informants, or collaborators operating in a coordinated network of espionage or intelligence within a foreign state; a local agency or branch representing the hidden or official interests of an external power. In a historical sense, the term often describes operational networks used for gathering strategic intelligence.
• Intelligence network variant — An archaic form or old variant for the noun agentură; the totality of secret agents, informants, or collaborators in a spy network operating within a state; also, a local office, agency, or branch representing the official or hidden interests of a foreign power. The term is frequently used in 19th and 20th-century diplomatic and political documents.
• Arcani — A term designating a special unit of spies, scouts, or secret agents within the Roman army, primarily active in the province of Britannia during the 3rd and 4th centuries. Their structural role involved infiltrating enemy territories beyond Hadrian's Wall, gathering tactical intelligence, and reporting barbarian tribal movements, before being disbanded due to their complicity in the 'Great Conspiracy' of 367 AD.