Flags of the Ottoman Empire

The Ottoman Empire used various flags and naval ensigns during its history. The crescent and star came into use in the second half of the 18th century. A buyruldu (decree) from 1793 required that the ships of the Ottoman Navy were to use a red flag with the star and crescent in white. In 1844, a version of this flag, with a five-pointed star, was officially adopted as the Ottoman national flag. The decision to adopt a national flag was part of the Tanzimat reforms which aimed to modernize the Ottoman state in line with the laws and norms of contemporary European states and institutions.
The star and crescent design later became a common element in the national flags of Ottoman successor states in the 20th century. The current flag of Turkey is essentially the same as the late Ottoman flag, but has more specific legal standardizations (regarding its measures, geometric proportions, and exact tone of red) that were introduced with the Turkish Flag Law on 29 May 1936. Before the legal standardization, the star and crescent could have slightly varying slimness or positioning depending on the rendition.
Pre-modern Ottoman armies used the horse-tail standard or tugh rather than flags. Such standards remained in use alongside flags until the 19th century. A depiction of a tugh appears in the Relation d'un voyage du Levant by Joseph Pitton de Tournefort (1718). War flags came into use by the 16th century. During the 16th and 17th centuries, Ottoman war flags often depicted the bifurcated Zulfiqar sword, often misinterpreted in Western literature as showing a pair of scissors.
The crescent symbol appears in flags attributed to Tunis from as early as the 14th century (Libro de conoscimiento), long before Tunis fell under Ottoman rule in 1574. But the crescent as a symbol also had 14th-century associations with the Ottoman military and millennium-long associations with the city of Istanbul, which became the Ottoman capital after its conquest in 1453. The Spanish Navy Museum in Madrid shows two Ottoman naval flags dated 1613; both are swallow-tailed, one green with a white crescent near the hoist, the other white with two red stripes near the edges of the flag and a red crescent near the hoist.
The star and crescent design appears on Ottoman flags beginning in the late 18th or early 19th century. The white star and crescent moon with a red background was introduced as the flag of the Ottoman Empire in 1844.
It has been suggested that the star-and-crescent used in Ottoman flags of the 19th century had been adopted from the Byzantine. Franz Babinger (1992) suggests this possibility, noting that the crescent alone has a much older tradition also with Turkic tribes in the interior of Asia. The crescent and star is found on the coinage of Byzantium since the 4th century BC and was depicted on Byzantine Empire's coins and shields of Christian warrior saints till the 13th century. Parsons (2007) notes that the star and crescent was not a widespread motive on the coinage of Byzantium at the time of the Ottoman conquest. Turkish historians tend to stress the antiquity of the crescent (not star-and-crescent) symbol among the early Turkic states in Asia.
The imperial standard displayed the sultan's tughra, often on a pink or bright red background.
The standard used by the last Caliph, Abdulmejid II (between 19 November 1922 – 3 March 1924) consisted of a green flag with a star and crescent in white on a red oval background within a rayed ornament, all in white.
The Ottoman army often used verses from the Quran and Shahada on their flags. This tradition continued during the First World War. When Ottoman Turkey joined the war on the side of the Central Powers in 1914, it declared a jihad against the Entente States. The modern Ottoman Turkish army used the Ottoman state coat of arms on one side of their standard regimental flags and Shahada on the other. The Ottoman regimental flags consisted of gold writings and the state emblem on a red background. After the empire was abolished in 1922, this practice continued for a while in modern Turkey.