Operation Arsenal, code name: "Meksyk II" (Polish: Akcja pod Arsenałem) was the first major operation by the Szare Szeregi (Gray Ranks)  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".

The successfully conducted operation led to the release of Jan Bytnar and 24 other prisoners, including another Storm Group troop leader, Henryk Ostrowski "Henryk", and 6 women, in an attack on the prison van that was taking the inmates from Pawiak Prison to Gestapo Headquarters at Szucha Avenue. 

Sadly, Bytnar himself died four days later on account of injuries sustained due to German torture. Both of his interrogators, identified as Hubert Schulz and Ewald Lange, were assassinated by Szare Szeregi within two months. 

The operation was commemorated in the book “Kamienie na Szaniec” (“Stones for the rampart”) by Aleksander Kamiński, describing the story of “Rudy”, “Zośka” and “Alek.” It was also presented in the movie “Operation Arsenal” from 1978 and the film “Kamienie na Szaniec” from 2014, based on Mr Kamiński’s book.