The siege of Baghdad (1733) was a relatively short but intense siege of Ottoman-held Baghdad by the Persian army under Nader. The outcome was determined not at Baghdad but ultimately far to the north near Samara where a large relief force commanded by the Topal Pasha inflicted a decisive defeat on Nader's Persian army (the only battlefield defeat of Nader's career). The Persian besiegers were forced away with the loss of most of their equipment and saving a much exhausted garrison desperate for relief.
Ahmad Pasha, the governor of the Baghdad Eyalat, cautiously held to the left bank of the Tigris knowing what a formidable barrier it posed to the invading Persian army. Nader camped on the east side and resorted to a ruse whereby he would fool the Ottomans by keeping a large portion of his men in and around the camp but only to gather a small hand-picked group of soldiers to march north under the cover of night.
On February 15 Nader crossed the Tigris with 2,500 and immediately moved south with another 1,500 men managing to make the crossing to follow Nader just before the bridge over the river collapsed into it. Ahmad Pasha accelerated his force up the Tigris as soon as he heard of the Persian contingent's presence on the left bank of the river. Nader's small band included three fowj of Kurdish (each "fowj" being a unit of 1,000 soldiers), Turcomen and Abdali Afghan troops which he formed up against a formidable Ottoman assault containing artillery, cavalry and janissaries (infantry).
The Turcomen and Kurds were driven back but the Abdali held long enough for the 1,500 men that crossed the Tigris before the collapse of the bridge to come from the north. Nader drew them up in formation and fed them into the battle, gradually pushing Ahmad pasha's line back until it was broken and the remnants fled towards Baghdad leaving many guns and corpses behind. Nader ordered some of the Kurds and Turcomen hanged for their cowardice in the face of danger and conversely rewarded the Abdali.
The environs of Baghdad were soon swarming with Persian soldiers as they joined their comrades from the east bank of the Tigris and began a colossal effort constructing 2,700 towers around the perimeter of the city. It is estimated that a total of 300,000 Persians were besieging the walls of Baghdad although just a 100,000 of them were soldiers.
Sin embargo, el resultado del asedio se decidió muchas millas al norte de Bagdad, cerca de una ciudad llamada Samarra , donde Estambul había enviado el mejor ejército que pudo reunir bajo el mando del mejor general que tenía: Topal Osman Pasha . Nader marchó arrogantemente hacia el norte para atacar a las fuerzas de socorro otomanas en lugar de elegir un campo de batalla adecuado para una batalla defensiva. El resultado fue uno de los enfrentamientos más sangrientos de las campañas de Nader, en el que casi la mitad del ejército persa quedó "fuera de combate" e incluso los otomanos perdieron una cuarta parte de su ejército, dejando una aterradora cifra de 20.000 hombres como víctimas de la debacle.
De hecho, la batalla fue tan aplastantemente decisiva que obligó a los persas a abandonar el Iraq otomano, salvando a Bagdad de una captura segura por parte de Persia. Aunque Nader se recuperaría milagrosamente de su derrota, destruyendo el ejército de Topal Pasha, aún así no logró capturar Bagdad en su campaña posterior (principalmente debido a una insurrección en el sur de Persia que requirió su presencia inmediata).