The Greco-Turkish War of 1897 or the Ottoman-Greek War of 1897, also called the Thirty Days' War and known in Greece as the Black '97 or the Unfortunate War, was a war fought between the Kingdom of Greece and the Ottoman Empire. Its immediate cause involved the status of the Ottoman province of Crete, whose Greek-majority population had long desired union with Greece. Despite the Ottoman victory on the field, an autonomous Cretan State under Ottoman suzerainty was established the following year, with Prince George of Greece and Denmark as its first High Commissioner.

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.