In his new capacity, Isopescu-Grecul favored an understanding with Hungarian conservatives during the War of 1919, in which Romania defeated the Hungarian Soviet Republic. In his indirect contacts with József Somssich, the conservative Minister of Foreign Affairs, he proposed a détente, noting that both their countries were threatened by Slavic encroachment. Reportedly, he described the Romanian military's conduct in Hungary as "most regrettable", and complained to his own co-nationals about the style of Romanian administration in the new regions. He also circulated rumors about a possible Hungarian–Romanian federation, as proposed to him by Hungarian landowners.