In this task, you are given a question and a context passage. You have to answer the question based on the given passage.
Example: what is the first event mentioned?, Context: The Russian Revolution is the series of revolutions in Russia in 1917, which destroyed the Tsarist autocracy and led to the creation of the Soviet Union. Following the abdication of Nicholas II of Russia, the Russian Provisional Government was established. In October 1917, a red faction revolution occurred in which the Red Guard, armed groups of workers and deserting soldiers directed by the Bolshevik Party, seized control of Saint Petersburg (then known as Petrograd) and began an immediate armed takeover of cities and villages throughout the former Russian Empire.
Example solution: Russian Revolution
Example explanation: This is a good example, and the Russian Revolution is the first event mentioned.

Problem: After which event did Ottoman forces capture Calafat?, Context: Following the Ottoman ultimatum in September 1853, forces under the 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 following 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 them on 6 January 1854. The battle began when the Russians made a move to recapture Calafat. Most of the heavy fighting, however, took place in and around Chetatea until the Russians were driven out of the village. Despite the setback at Chetatea, on 28 January 1854, Russian forces laid siege to Calafat. The siege would continue until May 1854 when the Russians lifted the siege. The Ottomans would also later beat the Russians in battle at Caracal.:130–43
Solution: the Ottoman ultimatum in September 1853