He was a key entity in the conversion of the Popular Front's militias into a disciplined standing army, the Spanish Republican Army, able to fight Franco's Nationalist Front.

[6] Antonio Cordón also actively contacted with the Soviet Union over the provision of war materials, including T-26 light tanks and Polikarpov I-16s.

Finalizing the war, Antonio Cordón immigrated to the Soviet Union and formed part of the Central Committee of the Communist Party, working closely with Dolores Ibárruri and Santiago Carrillo, who he coincided in Paris with for a short while.

He also had close relations with figures such as Rafael Alberti and Teresa León.

After Casado's coup, on 6 March 1939 he fled Spain from the Monòver aerodrome with Negrín and Ibárruri.