As the Bolsheviks took power in Russia and began negotiations for ending hostilities, Romania signed an armistice in December 1917 and the military mission had to be sent back to France.
[6] On the way home from his visit to Petrograd in early 1917, shortly before the Fall of the Tsar, General de Castelnau stopped off for talks with Berthelot, and was told that the Romanian army could not be ready before 15 May.
[7] In August 1917 Foch sent General Albert Niessel (a Russian speaker and formerly commander of IX Corps), on a mission to Russia (by then a republic under the Provisional Government) in the hope of repeating Berthelot's success there.
[9] However, when the Bolsheviks began negotiations to take Russia out of the war which resulted in their ceasefire agreements, Romania, surrounded by the Central Powers, had to sign an armistice on 9 December 1917, followed by a peace treaty on 7 May 1918.
At Berthelot's suggestion, Britain and France issued a statement that Romania had fought hard, and had been overcome by circumstances beyond her control and that the imposed peace treaty would be disregarded by the Allies.