In Paris, after entering the leadership of its affiliated National Front of Medical Students, in 1944 Riffaud joined the Communist Party (PCF) and its resistance group Francs-tireurs et partisans (FTP).
[8] In June, the Waffen-SS massacred 642 civilians in a village from Riffaud's childhood, Oradour-sur-Glane,[7] prompting the FTP Resistance to direct its members to each kill a German.
I wanted to do more than simply harangue people in queues, telling them the truth of what was happening and I was cross at being told always to carry weapons across town for the men to use, so I asked for permission to use a gun myself.
[8] On 23 July 1944, in broad daylight on a bridge overlooking the river Seine, she approached a lone German NCO and when he turned to face her ("it was important to me not to shoot him in the back”) she shot him twice in the temple.
[2] Four days later she was freed in a prisoner exchange negotiated by the Swedish consul Raoul Nordling with Wehrmacht's last Paris commander, Dietrich von Choltitz.
On 23 August, in command of four men, and with the support of railway workers she trapped a train carrying loot and munitions in the Buttes-Chaumont tunnel and secured the surrender of the 80 German soldiers aboard.
She had hoped to finish the war with the rest of her resistance group, now part of the regular French army, but, at a time when women in France did not yet have the right to vote, she was told that she did not have her father's permission.
[8] Left behind in Paris, she found herself acting as a guide to the city for a young American soldier, the future singer Sammy Davis Jr..[13]: 108–109 Riffaud said she owed her life to the surrealist poet Paul Éluard who encouraged her to write.
[15] While working as a journalist for Ce soir, a newspaper run by Aragon,[14] in 1945 Riffaud published her first poetry collection, Le Poing Fermé (The Clenched Fist), with a preface by Éluard and a sketch portrait of her by Picasso on the cover.
She had hosted an Algerian high school student, the future writer and journalist Kateb Yacine, who bore witness to massacres in Algeria that had followed the Muslim demonstrations of 8 May 1945.
[20] In Paris, Riffaud supported the Movement for the Triumph of Democratic Liberties (MTLD), led by Messali Hadj, and their banned demonstration of 14 July 1953 which the police dispersed with deadly fire.
[21] In 1952, and again 1954, La Vie Ouvrière, the press organ of the labour federation CGT, sent Riffaud to Algeria where her reports bore witness to the political and social tensions rising in advance of the Algerian insurrection.
A few months later, in November 1946, she published a poem in La Vie Ouvrière decrying the French bombardment of Haiphong (the opening salvo of the First Indochina War).
[13]: 200 In Berlin, reporting on the 1951 World Festival of Youth and Students, Riffaud met and fell in love with the poet (and later, North Vietnamese Vice-State President) Nguyễn Đình Thi.
It was only in 1994, on the 50th anniversary of the Liberation, that a former comrade, Raymond Aubrac, persuaded her to honour the memory of her friends who had died in the struggle by speaking publicly of her experience of the Resistance:[6][28] That year a curator found some of her poetry, partly written in prison, and convinced her to write a memoir giving them context; this resulted in the book On l'appelait Rainer.
The occasion was marked by a visit from Vietnamese ambassador to France[31] and the release of the final volume of her graphic war-time memoir, Madeleine, Résistante, created with artist Dominique Bertail and writer Jean-David Morvan.