The previous incarnation of Croat-Serb cooperation in the historical Croatian lands under Austro-Hungarian rule had happened sixty years earlier in the Illyrian movement; its proponents advocated the unification of South Slavs in the Habsburg monarchy under an autonomous Croatian kingdom.[2][3] The idea came to an abrupt end with the revolution of 1848.
The underlying reason for the formation of the Coalition in the early 1900s was the mass realization that the Hungarian and Austrian governments as well as the Italian irredentists all profit from the divisions between the Croats and the Serbs. This became particularly apparent following the popular demonstrations against the Croatian banKhuen Hedervary in 1903, where the masses of Croat peasants were joined by Serb peasants, and achieved a greater effect. The Coalition itself originated in the Resolutions of Rijeka and Zadar of October 1905, wherein the groups of individual Croat and Serb parliamentary representatives formulated requests for the improvement of Croat and Serb national interests, respectively, focused on the integration of Dalmatia with Croatia-Slavonia[4] and the elevation of the country's position within the monarchy.
The parties which initially joined the Coalition included: Croatian Party of Rights, Croatian People's Progressive Party (the liberals), Serb People's Independent Party, Serb People's Radical Party and Social Democratic Party of Croatia and Slavonia.[5] By this time, the Croatian Party of Rights had also included members of the Independent People's Party, who had previously split from the pro-Hungarian mainstream faction of the People's Party. On December 11, 1905, the Coalition representatives published their political programme. Its declaration promoted equality between Serbs and Croats, constitutional rule and civic rights, local autonomy, and reforms of the Nagodba, the Austro-Hungarian pact which governed Croatia's political status.[6]
In the 1906 Croatian parliamentary election they won a majority of seats in the Parliament (Sabor) of the Kingdom of Croatia-Slavonia.[5] The coalition supported the separation of church and state, opposing clergy participation in politics.[5] Its initial goal was to get rid of the governing National party,[7] seeing German-Austrian domination as a threat, while long-term it sought the unification of South Slavs.[5]
The Social Democrats and Serb Radicals would later break away from the Coalition, while in 1910 Croatian Party of Rights and the Croatian People's Progressive Party merged into the Croat Independent Party (Hrvatska samostalna stranka).
In 1908, the Coalition won the election again, but it also came under attack from the Vienna Imperial Court, which accused its leadership of grand treason. In 1909, 53 members of the Serb Independent Party were put on trial for collaboration with Serbia.[8] In this politically motivated trial, known as the Agram Trial, the defendants were found guilty with flimsy evidence and given prison sentences.[9][10] As the international political situation shifted (the Serbian government recognized Austria-Hungary's annexation of Bosnia-Herzegovina), the members were pardoned by Franz Joseph in 1910.[9][10] This came at a cost of having to marginalize their leader Frano Supilo and having to temper their criticism of the government in the Kingdom of Hungary. Svetozar Pribićević became the new leader and closed a formal agreement with the government in 1913. The Coalition continued to win elections in 1910 and 1913. It dominated Croatian South Slavic politics throughout World War I.[5] While the leaders of the Coalition continued to participate in Austro-Hungarian politics, they also participated in the Yugoslav Committee during World War I.