When the World War I broke out, the Radical Party ceased operating along with all other Serbian organizations in Austria-Hungary. Its leaders spent the subsequent war years in the internment. The above mentioned Radicals reactivated during a rather tumultuous autumn in 1918. The Radicals from Srem, led by Žarko Miladinović, started their cooperation with the National Council from Zagreb. Their main activities were to protect the Serbian national interests and to demand an unconditional unification with Serbia. The Radical leaders from Bačka, Baranja and Banat headed by Jaša Tomić were very cautious in their public appearances because they were not sure of the future of the Hungarian borders. It was not until the beginning of November that the Serbian National Board was formed. A number of such bodies were formed in many places all over Vojvodina. The culmination of these activities was the Great National Assembly held in Novi Sad on November 25th. Due to the Radicals and Jaša Tomić especially, a decision to annex Bačka, Baranja and Banat to Serbia was made in this Assembly: they decided to join them directly to Serbia and not through the National Council in Zagreb, which was the other alternative. A day before the above mentioned event, representatives of the National Council from Srem also expressed their support to a direct unification with Serbia at their meeting held in Ruma.
