In the meantime, the fall of Bucharest had left Romania divided: King Ferdinand, his government, and the army proceeded to Western Moldavia, where they continued resistance; in the Wallachian south, Conservative Lupu Kostaki and his allies tolerated, or collaborated with, the German occupation. Mariu was one of Kostaki's associates, and, in January 1918, was appointed secretary of the Wallachian Bishopric, an Orthodox institution. His Catholicism having been revealed to the public, he was forced two resign a few days into his office. A few weeks after, Marghiloman was called upon to form a cabinet and negotiate a peace with the Central Powers (which was signed in May 1918). Mariu believed that Marghiloman was a godsend for Romania: "he managed to defend the dynasty and protect the army from being disarmed". He ran in the 1918 election, taking a seat in Senate for Ilfov County, and resuming his work for the unification of churches. His major effort was in supporting the Romanians of Northern Dobruja, which Romania had effectively ceded to Greater Bulgaria. Mariu Theodorian suggested that Orthodox Romanians, forcefully integrated into Bulgarian Orthodoxy, protect themselves by mass-converting to Catholicism.