Pushed out of political affairs by the PNL's leadership before the March 1911 elections, Diamandy focused on his activity as a comedic writer. He returned into the mainstream during the early stages of World War I, when Romania preserved a policy of neutrality under PNL Prime Minister Ion I. C. Brătianu. The latter selected Diamandy as his semi-official envoy to Entente countries, where he negotiated deals and treaties of mutual assistance. He was again elected to Chamber in 1914, where he showed himself to be a cautious supporter of an alliance between Romania and the Entente. In summer 1916, Brătianu agreed to a political and territorial deal, and Romania entered the war as an Entente country. Diamandy fought in the subsequent campaign, but was soon hospitalized for a heart condition.