In the summer of 1917 Besteiro became involved in the organization of a political strike in Spain. The strikers demanded the establishment of a provisional republican government, elections to a constituent Cortes and action to deal with inflation. In Madrid members of the strike committee, including Besteiro and Francisco Largo Caballero, were arrested and sentenced to life imprisonment.
Besteiro was released in 1918 and was later elected to the Cortes as deputy for Madrid. Besterio also became president of the Socialist Party (PSOE) and the the UGT. After the fall of Alfonso XIII democracy was restored in Spain. Following parliamentary elections Besteiro was elected president of the Constituent Cortes. Besteiro opposed the growing radicalization of the trade union movement and in January 1934 resigned as president of the UGT.
Besteiro argued against the inclusion of the Communist Party in the Popular Front movement. However, the views of Francisco Largo Caballero and Indalecio Prieto prevailed and Besteiro lost his power base in the Socialist Party. Besteiro remained a popular figure in Madrid and in the 1936 elections he won the highest number of votes of any candidate in the city.
In the early months of the Spanish Civil War Besteiro opposed the introduction of extreme left-wing policies. This made him even more isolated in his party and held only a minor municipal post in Madrid throughout the war.
In May 1937 Besteiro agreed to go to London to meet Anthony Eden where he explored the possibility of British mediation between the Republicans and the Nationalists. He also visited Leon Blum in France, but although both men were sympathetic they were unable to persuade General Francisco Franco to agree to peace talks.
Besteiro grew increasingly disillusioned with the policies of Juan Negrin. When President Manuel Azaña refused to dismiss him, Besteiro joined Segismundo Casado, commander of the Republican Army of the Centre, and disillusioned anarchist leaders, to establish an anti-Negrin National Defence Junta.
On 6th March 1939 José Miaja in Madrid joined the rebellion by ordering the arrests of Communists in the city. Negrin, about to leave for France, ordered Luis Barceló, commander of the First Corps of the Army of the Centre, to try and regain control of the capital. His troops entered Madrid and there was fierce fighting for several days in the city. Anarchists troops led by Cipriano Mera, managed to defeat the First Corps and Barceló was captured and executed.
Segismundo Casado now tried to negotiate a peace settlement with General Francisco Franco. However, he refused, demanding an unconditional surrender. Members of the Republican Army still left alive, were no longer willing to fight and the Nationalist Army entered Madrid virtually unopposed on 27th March 1939.
Besteiro refused to leave Spain with other left-wing politicians when it became clear that the Nationalists would win the Spanish Civil War. He told the socialist daily, La Voz, "The great majority, the masses, they can't leave, and I, who have always lived with the workers, will continue with them and with them I will stay. Whatever is their fate will be mine"
Despite Besteiro's attempts to negotiate an end to the war he was arrested and on 8th July 1939 he faced a court martial for the alleged crime of "military rebellion". He was found guilty and sentenced to thirty years' imprisonment. Julian Besteiro died of tuberculosis in Carmona Prison on 27th September, 1940.
Just before the war broke out I interviewed Julian Besteiro, gentle, soft-spoken philosopher who heads the Moderate Socialist party in Spain. The interview was held in the modest little home Professor Besteiro built near the end of the Castellana boulevard in Madrid. A socialist congress was scheduled to be held in August (1936) and a bitter fight was pending for leadership of the party. It was split three ways, with Francisco Largo Caballero heading the extreme Left group, Indalicio Prieto the center group, and Besteiro the Right faction. I wanted Besteiro's views on the outcome of the congress.
"I do not think I have a chance," he told me. "Since the elections, the extreme Left has won away most of my followers. Prieto is clever and is holding out to have the congress staged in Asturias, where his influence is greatest. If he succeeds, he probably will win, because relatively few delegates can make such a long trip. I think Largo Caballero probably will have things his own way, however."
"And after that?" I prompted.
"Who can say? Largo swings toward Communism, but the Spaniard is too much of an individualist to submit long to regimentation. Stormy days are ahead for Spain. I am planning to retire from politics if they take a too decided Left trend, and devote my remaining years to my teaching at the university."
The congress never was held because the war broke a month before it was to open. Besteiro's prophecies have in a large measure come true. Spain's "stormy days" were more stormy than he ever imagined they would be. The calm has not yet come. But the great mass of the people in Loyalist Spain is sick of the war and will welcome any solution which brings peace. The great majority of the masses is hostile to Fascism. It is equally hostile to violent ideologies which justify murder and destruction. Those living deep within Loyalist territory are powerless even to suggest such a thing as surrender or arbitration, but the relative ease with which Franco captured Bilbao and Santander was indicative of an increasing willingness to capitulate under any terms.