Shortly after the outbreak of World War I, with Romania still neutral territory, the Francophile Rosetti campaigned for Romania to join the Entente Powers, and tackled the issue during debates at the Romanian Writers' Society. However, he earned recognition for his court defense of Hasan Tahsin, would-be assassin of the pro-Entente campaigners Noel and Charles Buxton. In the end, Romania joined the Entente, and Rosetti was called under arms. Unexpectedly, he was moved to a horse artillery unit, but was shielded from active service by General Alexandru Averescu, and only assigned to give patriotic speeches to his troops on the front line. During the subsequent siege of Bucharest, Rosetti was at Periș with the staff of Constantin Prezan—Ion G. Duca, who joined him there, recalled that he "made himself look important". His subordinates included Cristache Ciolac, famous in civilian life as a "Lăutar" performer, and honored by Rosetti with a sonnet.