Galicia on 1 July. In order to counter this success, six German divisions mounted a counterattack on 18 July that tore a hole through the Russian front through which they sliced southward toward Tarnopol. The ensuing German advance threatened to encircle the Russian attackers, thereby causing them to retreat. At the end of August the advancing Central Powers stopped at the frontier of Moldavia. To keep up the pressure and to seize ground he intended to keep, Hindenburg shifted north to the heavily fortified city of Riga (today in Latvia) which has the broad Dvina River as a moat. On 1 September the Eighth Army, led by Oskar von Hutier, attacked; Bruchmüller's bombardment, which included gas and smoke shells, drove the defenders from the far bank east of the city, the Germans crossed in barges and then bridged the river, immediately pressing forward to the Baltic coast, pocketing the defenders of the Riga salient. Next a joint operation with the navy seized Oesel and two smaller islands in the Gulf of Riga. The Bolshevik revolution took Russia out of the war, and an armistice was signed on 16 December. The Reichstag peace resolution Hindenburg detested Chancellor Bethmann Hollweg for arguing against unrestricted submarine warfare. Then in July the Reichstag to debated a resolution for peace without "annexations or indemnities". Colonel Bauer and the Crown Prince hurried to Berlin to block the move. The minister of war urged Hindenburg and Ludendorff to join them, but when they arrived the Kaiser told them that "there could be no justification for their presence in Berlin". They should "return in haste to Headquarters where they certainly would be much better occupied." In a letter to the Emperor dated 12 July 1917, Ludendorff threatened to resign, and Hindenburg joined in the ultimatum. The Kaiser declined to accept. By then the majority parties in the Reichstag saw Bethmann Hollweg as an unacceptable negotiator for peace because he had been chancellor too long and was too weak in his dealings with the Supreme Army Command. The crisis was resolved when Bethmann Hollweg voluntarily resigned. Ludendorff and Bauer wanted to replace both the Kaiser and chancellor by a dictator, but Hindenburg would not agree. Many historians believe that in fact Ludendorff assumed that role. The Reichstag passed a modified resolution calling for "conciliation" on 19 July, which the new chancellor Georg Michaelis agreed to "interpret". The resolution became