The lack of consensus on Portugal's participation in the war made possible the emergence of two dictatorships, led by Pimenta de Castro (January – May 1915) and Sidónio Pais (1917–1918), called the President-King.

Sidónio Pais also attempted to restore public order, turning the republic into a more acceptable model for the monarchists and Catholics who still remained a political force.

This military victory allowed the Portuguese Republican Party return to government and emerge triumphant in the elections that took place during that year, winning them by an absolute majority.

Several different formulas were tried, including single-party governments, coalitions and presidential executives but none of them had any effect, causing the use of force to be considered "the only way" for the opposition to prevail if it wanted to enjoy the fruits of the can.

Historian Stanley Payne points out, "The majority of Republicans took the position that Catholicism was the number one enemy of individualist middle-class radicalism and must be completely broken as a source of influence in Portugal.

"[3] Under the leadership of Afonso Costa, the Minister of Justice, the revolution immediately targeted the Catholic Church; the provisional government began devoting its entire attention to an anti-religious policy, in spite of the disastrous economic situation.

[5] On 24 May 1911, Pope Pius X issued the encyclical Iamdudum which condemned the anticlericalism of the new republic for its deprivation of religious civil liberties and the "incredible series of excesses and crimes which has been enacted in Portugal for the oppression of the Church.

Finally, on 28 May 1926 the Portuguese Revolution of 1926 took place, a coup d'état by the armed forces supported by almost all the political parties that had given up on their plans to establish a stable government and conferred that mission on the army.

With this began a military dictatorship that would maintain the formal structure of the Republic, but whose authoritarianism would slowly lead to the autocratic regime known as Estado Novo in the year 1932.

In a period of 16 years (1910–1926) Portugal had 8 Presidents of the Republic, 1 Provisional Government, 45 Prime Ministers and 1 Constitutional Junta: Most historians have emphasized the failure and collapse of the republican dream by the 1920s.

José Miguel Sardica in 2011 summarized the consensus of historians: "… within a few years, large parts of the key economic forces, intellectuals, opinion-makers and middle classes changed from left to right, trading the unfulfilled utopia of a developing and civic republicanism for notions of "order," "stability" and "security."

"[7]Sardica, however, also points up the lasting effects of the republican experiment: "Despite its overall failure, the First Republic endowed twentieth-century Portugal with an insurpassable and enduring legacy—a renewed civil law, the basis for an educational revolution, the principle of separation between State and Church, the overseas empire (only brought to an end in 1975), and a strong symbolic culture whose materializations (the national flag, the national anthem and the naming of streets) still define the present-day collective identity of the Portuguese.