revised. Russia was to abandon any claim granting it the right to interfere in Ottoman affairs on behalf of Orthodox Christians. Those points, particularly the third, would require clarification through negotiations, which Russia refused. The allies, including Austria, therefore agreed that Britain and France should take further military action to prevent further Russian aggression against the Ottomans. Britain and France agreed on the invasion of Crimea as the first step. Battles Danube campaign The Danube campaign opened when the Russians occupied the Danubian Principalities of Moldavia and Wallachia in July 1853, which brought their forces to the north bank of the River Danube. In response, the Ottoman Empire also moved its forces up to the river, establishing strongholds at Vidin in the west and Silistra in the east, near the mouth of the Danube. The Ottoman move up the River Danube was also of concern to the Austrians, who moved forces into Transylvania in response. However, the Austrians had begun to fear the Russians more than the Ottomans. Indeed, like the British, the Austrians were now coming to see that an intact Ottoman Empire was necessary as a bulwark against the Russians. Accordingly, Austria resisted Russian diplomatic attempts to join the war but remained neutral during the Crimean War. After the Ottoman ultimatum in September 1853, forces under Ottoman General Omar Pasha crossed the Danube at Vidin and captured Calafat in October 1853. Simultaneously, in the east, the Ottomans crossed the Danube at Silistra and attacked the Russians at Oltenița. The resulting Battle of Oltenița was the first engagement since the declaration of war. The Russians counterattacked but were beaten back. On 31 December 1853, the Ottoman forces at Calafat moved against the Russian force at Chetatea or Cetate, a small village nine miles north of Calafat, and engaged it on 6 January 1854. The battle began when the Russians made a move to recapture Calafat. Most of the heavy fighting took place in and around Chetatea until the Russians were driven out of the village. Despite the setback at Chetatea, Russian forces on 28 January 1854 laid siege to Calafat. The siege would continue until May 1854 when it was lifted by the Russians. The Ottomans would also later beat the Russians in battle at Caracal. In early 1854, the Russians again advanced by crossing the River Danube into the Turkish province of Dobruja. By April 1854, the Russians