In 1940 her father who was a mining engineer died and the three sisters had to work, forcing Carla Capponi to abandon her studies of Law.

[1] On 19 July 1943, immediately after the bombing of San Lorenzo, Carla rushed to the Policlinico Hospital in search of her mother and remained there as a volunteer;[2] subsequently she allows clandestinely communist activists to gather in her apartment in front of the Trajan's Forum, including Gioacchino Gesmundo, Luciano Lusana, Adele Bei, Carla Angelini and Mario Leporatti.

A comrade in the struggle described her as "this young blonde woman who went out at night to shoot Germans... with arms in hand, first among the first, she participated in dozens of actions, distinguishing herself in a superb way."

[1] Among her first major actions was the assassination of a German officer leaving the Hotel Excelsior carrying a briefcase with defence plans for the city.

It was raining and tears were streaming down my face... After getting over the initial shock, especially since many of our comrades were being arrested and tortured, all our scruples were replaced by sheer determination to fight for our cause.

"During the Via Rasella attack on 23 March 1944, she became a vice-commander of a Gruppi di Azione Patriottica (GAP; "Patriotic Action Groups") squad.