National flag
History

Historically, flags originated as military standards, used as field signs. Throughout history, various examples of such proto-flags exist: the white cloth banners of the Zhou dynasty 's armies in the 11th century BC, the vexillum standards flown by the armies of the Roman Empire, the Black Standard famously carried by Muhammad which later became the flag of the Abbasid Caliphate, and the various " Raven banners " flown by Viking chieftains. Angelino Dulcert published a series of comprehensive Portolan charts in the 14th century AD, which famously showcased the flags of several polities depicted – although these are not uniformly "national flags", as some were likely the personal standards of the respective nation's rulers.

The practice of flying flags indicating the country of origin outside of the context of warfare became common with the maritime flag. During the 13th century, the republics of Genoa and Venice both used maritime flags; William Gordon Perrin wrote that the republic of Genoa was "one of the earliest states to adopt a national flag".

The current design of the flag of the Netherlands originates as a variant of the late 16th century orange-white-blue Prinsenvlag ("Prince's Flag"), that was used in the Dutch War of Independence (1568–1648), evolving in the early 17th century as the red-white-blue Statenvlag ("States Flag"), the naval flag of the States-General of the Dutch Republic, making the Dutch flag perhaps the oldest tricolour flag in continuous use, although standardisation of the exact colours is of a much later date.

During the Age of Sail in the early 17th century, the Union Jack finds its origins, when James VI of Scotland inherited the English and Irish thrones (as James I). On 12 April 1606, the new flag representing this regal union between England and Scotland was specified in a royal decree, according to which the flag of England (a red cross on a white background, known as St George's Cross), and the flag of Scotland (a white saltire on a blue background, known as the Saltire or St Andrew's Cross), would be joined, forming the flag of Great Britain and first Union Flag - but then without the red Cross of St. Patrick. It continued in use until 1 January 1801, the effective date of the legislative union of Great Britain and Ireland, when the Cross of St. Patrick (a red diagonal cross on white) was incorporated into the flag, giving the Union Jack its current design.

With the emergence of nationalist sentiment from the late 18th century national flags began to be displayed in civilian contexts as well. Notable early examples include the US flag, which was first adopted as a naval ensign in 1777 but began to be displayed as a generic symbol of the United States after the American Revolution, and the French Tricolor, which became a symbol of the Republic in the 1790s.

Most countries of Europe standardised and codified the designs of their maritime flags as national flags, in the course of the 19th and early 20th centuries. The specifications of the flag of Denmark, based on a flag that was in continuous use since the 14th-century, were codified in 1748, as a rectangular flag with certain proportions, replacing the variant with a split. The flag of Switzerland was introduced in 1889, also based on medieval war flags.

In Europe, the red-white-blue tricolour design of the flag of the Kingdom of the Netherlands became popular, since it was associated with a republican form of government through that country's long war of independence against the Spanish Crown. That association was greatly reinforced after the French Revolution (1789), when France used the same colours, but with vertical instead of horizontal stripes. Other countries in Europe (like Ireland, Italy, Romania and Estonia) and in South and Central America selected tricolours of their own to express their adherence to the principles of liberty, equality, and fraternity as embodied in the French flag.

The Ottoman flag (now the flag of Turkey) was adopted in 1844. Other non-European powers followed the trend in the late 19th century, the flag of Great Qing being introduced in 1862, that of Japan being introduced in 1870. Also in the 19th century, most countries of South America introduced a flag as they became independent (Peru in 1820, Bolivia in 1851, Colombia in 1860, Brazil in 1822, etc.)

Currently, there are 193 national flags in the world flown by sovereign states that are members of the United Nations.
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