In August 1916, upon Romania’s entry into World War I, Samsonovici was advanced to lieutenant colonel and made and made chief of staff of an infantry division. As such, he coordinated offensive and defensive moves around Ghimeș, Brețcu, Târgu Secuiesc, Miercurea Ciuc, Vlăhița and Odorheiu Secuiesc. He was also active on the Trotuș and Uz valleys; after two weeks of heavy fighting, the Austro-Hungarian Army was prevented from taking Comănești, Dărmănești and Bacău, withdrawing into a defensive posture. Finally, he was active along the Cricovul Sărat line. For his merits, Samsonovici was made a colonel in April 1917. As a staff officer, he played an important role in the Battle of Mărășești, drawing praise from commanders Eremia Grigorescu and Constantin Prezan.