The Arkhangelsk–Astrakhan line,[nb 1] or A–A line for short, was the military goal of Operation Barbarossa. It is also known as the Volga–Arkhangelsk line,[1] as well as (more rarely) the Volga–Arkhangelsk–Astrakhan line.[nb 2][2] It was first mentioned on 18 December 1940 in Führer Directive 21 (Fall Barbarossa) which enunciated the set goals and conditions of the German invasion of the Soviet Union, describing the attainment of the "general line Volga–Archangelsk" as its overall military objective.[3]