A delegate to the 1914 PSD Congress, Călin advocated a more militant party position on the agrarian issue, and was decisive in the adoption of neutrality as the party's stance towards World War I. In October 1915, at the Extraordinary PSD Congress, he prepared the main report, which commented on the attitude of the European socialist movement towards the war. The report, critical of the Bureau of the Second International, adopted the anti-militarist stance of the first Zimmerwald Conference, while at the same time providing that, were Romania to join the war, the socialists would take no action that would damage the government. The report was approved by a large majority. At the same Congress, Călin was also elected to the party's Executive Committee, along with Ecaterina Arbore, Alecu Constantinescu, Gheorghe Cristescu, I.C. Frimu, Dimitrie Marinescu, and Christian Rakovsky. During the following months, he took part in the organisation of various anti-war protests across the country.