The 31 March Incident (Turkish: 31 Mart Vakası or 31 Mart Olayı or 31 Mart Hadisesi or 31 Mart İsyanı) refers to the defeat of the Ottoman countercoup of 1909 by the Hareket Ordusu ("Army of Action"), which was the 11th Salonika Reserve Infantry Division of the Third Army stationed in the Balkans and commanded by Mahmud Shevket Pasha on 24 April 1909. The counter coup began on 31 March on the Rumi calendar, which was the official calendar of the Ottoman Empire, corresponding to 13 April 1909 on the Gregorian calendar now used in Turkey. The rebellion had begun on 13 April 1909 and was put down by 24 April 1909. Ottoman historiography link the two events under the name 31 March Incident but refers to the actions by the Hareket Ordusu, the subsequent restoration of the constitution for a third time (after earlier attempts in 1876 and 1908) and the deposition of Abdul Hamid II who was then replaced by his younger brother Mehmed V.
The Young Turk Revolution, which began in the Balkan provinces, spread quickly throughout the empire and resulted in the Sultan Abdul Hamid II announcing the restoration of the Ottoman constitution of 1876 on 3 July 1908. The Ottoman general election of 1908 took place during November and December of that year. The Senate of the Ottoman Empire reconvened for the first time in over 30 years on 17 December 1908. The Chamber of Deputies' first session was on 30 January 1909. The Ottoman counter-coup of 13 April 1909 was a rebellion by conservative reactionaries in Constantinople against the restoration of the constitutional system. The counter-coup attempted to put an end to the nascent Second Constitutional Era in order to re-affirm the position of the Sultan Abdul Hamid II as the absolute monarch. The counter-coup, was instigated among some parts of the army primarily by a certain Cypriot Islamic extremistDervish Vahdeti, who reigned supreme in Constantinople for a few days.