Task: Question Answering
Input (English): Passage: The Arabs and Turks, estimated at 15,000, made frequent attacks by day and night on the strongly entrenched Italian garrison in the southern suburbs of Benghazi. The four Italian regiments of infantry acted on the defensive and were supported by the San Marco and Agordat. The Italians rarely attempted a sortie. An attack of 20,000 Turkish and local troops was repulsed on November 30 with considerable losses. Shortly after this the garrison was reinforced by the 57th infantry regiment from Italy. The battleship Regina Elena also arrived from Tobruk. During the night of December 14 and 15 the Turks attacked in great force, but were repulsed with aid of the fire from the ships. The Italians lost several field guns. At Derna the Turks and Arabs were estimated at 3,500, but they were being constantly reinforced and a general assault on the Italian position was expected. The Italian and Turkish forces in Tripoli and Cyrenaica were constantly reinforced. The withdrawal of the Turks into the interior enabled them to reinforce their troops considerably. The cost of the war was defrayed chiefly by voluntary offerings from Muslims. Turkish officers and men, weapons, ammunition, and all kinds of supplies were constantly sent across the Egyptian and Tunisian frontiers, notwithstanding their neutrality. The Italians occupied Sidi Barrani on the coast between Tobruk and Solum to prevent contraband and troops from entering across the Egyptian frontier, while the naval blockaders guarded the coast and captured several sailing ships with contraband. 
Question: How many nights in December did the Turks attack in force? 
Answer type: Number 
Output (English): 2.