A Greek revolt, which further drained the Ottoman war effort, brought about a truce between the Ottoman Empire and Austria. Meanwhile, the Russians continued their advance when Suvorov captured the reportedly "impenetrable" Ottoman fortress of Ismail at the entrance of the Danube, in December 1790. A final Ottoman defeat at Machin (9 July 1791), coupled with Russian concerns about Prussia entering the war, led to a truce agreed upon on 31 July 1791. After the capture of the fortress, Suvorov marched upon Constantinople (present-day Istanbul), where the Russians hoped they could establish a Christian empire. However, as Prof. Timothy C. Dowling states, the slaughters that were committed in the ensuing period somewhat defiled Suvorov's reputation in many eyes, and there were allegations at the time that he was drunk at the siege of Ochakov. Persistent rumors about his actions were spread and circulated, and in 1791 he was relocated to Finland.