In 1922 he was part of the guard of Óscar Pérez Solís, Secretary General of the Spanish Communist Party (Partido Comunista Español, PCE).

[2] In 1932 the Spanish Communist Party made a major change in direction when it abandoned the Comintern slogan "Workers' and Peasants' Government" and adopted "Defense of the Republic".

[1] After the outbreak of Spanish Civil War (1936–1939), on 8 August 1936 he said clearly "We cannot talk today of the proletarian revolution in Spain, because the historical circumstances do not permit it."

The Stalinists did indeed provide substantial support for the Giral and Caballero governments, including important military aid from the USSR.

[4] President Francisco Largo Caballero appointed Hernández Minister of Education and Fine Arts on 4 September 1936.

The trigger was a disagreement in a cabinet meeting over the May Days violence in Barcelona, which the communists blamed on the Anarchist CNT and FAI and the POUM.

[8] Hernández was replaced by Segundo Blanco in a cabinet reshuffle in April 1938 and was appointed political commissar in the South Central area.

[11][8] When the Republican forces were defeated in the Battle of the Ebro (July–November 1938) and General Francisco Franco's troops reached the Mediterranean, Hernández stayed in Madrid with Pedro Checa, Luis Cabo Giorla, Isidoro Diéguez Dueñas and Antonio Mije while the main Communist leadership center was established in Barcelona.

The book revealed how Andrés Nin had been tortured and then killed, the Procès de Moscou tribunal and other aspects of Stalinist interference.