The Ottoman Army was the army of the Ottoman Empire after the country was reorganized along modern western European lines during the Tanzimat modernization period. It operated during the decline and dissolution of the empire, which roughly occurred between 1861 and 1918, the end of World War I for the Ottomans. The Crimean War was the first war effort in which the modern army took part in, proving itself as a decent force. The last reorganization occurred during the Second Constitutional Era.

The Tanzimat was a period of reform in the Ottoman Empire that began with the Gülhane Hatt-ı Şerif in 1839 and ended with the First Constitutional Era in 1876. The Tanzimat era began with the purpose not of radical transformation, but of modernization, desiring to consolidate the social and political foundations of the Ottoman Empire. It was characterised by various attempts to modernise the Ottoman Empire and to secure its territorial integrity against internal nationalist movements and external aggressive powers. The reforms encouraged Ottomanism among the diverse ethnic groups of the Empire and attempted to stem the rise of nationalism in the Ottoman Empire.