The Operation Arsenal, code name: "Meksyk II" () was the first major operation by the Szare Szeregi (Gray Ranks) Polish Underground formation during the Nazi occupation of Poland. It took place on March 26, 1943 in Warsaw. Its name was coined after the Warsaw Arsenal, in front of which the action took place. The plan was to free the troop leader Jan Bytnar "Rudy", who was arrested together with his father by the Gestapo. The operation was executed by 28 scouts led by Warsaw Standard Commander Stanisław Broniewski "Orsza". The initiator and the commander of the "Attack Group" was Tadeusz Zawadzki "Zośka".