The Treaty of Bucharest brought Romania into the war as an Entente ally, then its invasion by Germany. Again drafted as a Lieutenant, Blank enlisted in the newly formed Romanian Air Force. He was subsequently spotted at Iași, the provisional capital of a rump Romanian state. Argetoianu reports that wartime Iași was where Blank first earned the trust of Carol of Hohenzollern, the disgraced Romanian Crown Prince. Carol used Blank in his attempts to earn support from Prime Minister Alexandru Averescu. Also according to Argetoianu, Blank was also faking asthma attacks, which saw him relieved of his duties and sent to Paris. During the exodus of 1917, Blank sponsored Ioan Timuș's extended trip to Japan, asking him to act as an informant and documentarist of Japanese cultural norms, and "therefore of use to our country". One report by Alexandru Lapedatu suggests that Blank transited through Moscow, in the Russian Republic, where he personally witnessed the November Revolution. He was evicted "by some Englishmen" during the Red Guards' attack on Hotel Metropol.