Sesto San Giovanni was known as the 'Stalingrad' of Italy. At the beginning of the 20th century, factories such as Pirelli, Breda, Falck, Ercole and Magneti Marelli were based here, just north of Milan. In the 1920s they had a workforce of 45,000 workers (more than the residents of the municipality). The PCDL (Communist Party of Italy) had infiltrated a solid clandestine network there, structured on departmental and factory cells that had promoted protest demonstrations in 1930 and 1939.

In March 1943, it was from here that the first demonstrations of dissent against the war came, with the coordination of a unitary Inter-Enterprise Committee, which arose within the Breda after-workers' club. Over the course of 45 days, an open trade union reorganisation took place: on 26 July, the workers led the procession of celebrations for the fall of the regime; on 9 August they demonstrated despite the intervention of the police; on 8 September, they self-organised for the Resistance to the invasion.

Despite the German occupation and repression, the activity did not stop and even culminated in the general strike against the carovita of 12 to 18 December, which saw the total suspension of production. First the clandestine agitation committees, and then the company CLN were born, linked to the city CLN that arose at the beginning of 1944. The break-up of the Gap and the failure of the organised strike in March 1944 led to the arrest and deportation of many workers. Four of them were among those shot at Piazzale Loreto.

The movement resumed in the summer with the birth of the SAP, which gathered over a thousand men under the command of Vinicio Franchini. They carried out intense sabotage and propaganda activities, but also supported the population. Starting in March 1945, the Comando Piazza di Sesto was established, led by Aldo Melloni and Giovanni Sordi, who guaranteed the defence of the plant. The company formations dismantled a contingent of French collaborationists and arrested all the fascists. The agitation committees were transformed into internal committees and production was resumed within a few days.

Sesto suffered over 500 deportees, 200 of whom died, an additional 29 were shot in retaliation, 23 died in combat, and 4 were imprisoned.