Several countries (including the United Kingdom and the Soviet Union) have had unique flags flown by their armed forces, rather than the national flag.
Other countries' armed forces (such as those of the United States or Switzerland) use their standard national flag. The Philippines' armed forces may use their standard national flag, but during times of war the flag is turned upside down. Bulgaria's flag is also turned upside down during times of war. These are also considered war flags, though the terminology only applies to the flag's military usage.
Large versions of the war flag flown on the warships of countries' navies are known as battle ensigns. In war waving a white flag is a banner of truce.
Four distinctive African flags currently in the collection of the National Maritime Museum in Britain were flown in action by Itsekiri ships under the control of Nana Olomu during conflict in the late 19th century. One is the flag generally known as the Benin flag and one is referred to as Nana Olomu's flag.
The usage of flags spread from India and China, where they were almost certainly invented, to neighboring Burma, Siam, and southeastern Asia.
In antiquity, field signs or standards were used in warfare that can be categorized as vexilloid or "flag-like". Examples include the Achaemenid battle standard Derafsh Kaviani, and the standards of the Roman legions such as the eagle of Augustus Caesar's Xth legion, or the dragon standard of the Sarmatians; the latter was let fly freely in the wind, carried by a horseman, but judging from depictions it was more similar to an elongated dragon kite than to a simple flag.
During the High Middle Ages flags came to be used primarily as a heraldic device in battle, allowing more easily to identify a knight than only from the heraldic device painted on the shield. Already during the high medieval period, and increasingly during the Late Middle Ages, city states and communes such as those of the Old Swiss Confederacy also began to use flags as field signs. Regimental flags for individual units became commonplace during the Early Modern period.
During the peak of the age of sail, beginning in the early 17th century, it has been customary (and later a legal requirement) for ships to carry flags designating their nationality; these flags eventually evolved into the national flags and maritime flags of today. Flags also became the preferred means of communications at sea, resulting in various systems of flag signals; see, International maritime signal flags.
Use of flags outside of military or naval context begins only with the rise of nationalist sentiment by the end of the 18th century; the earliest national flags date to that period, and during the 19th century it became common for every sovereign state to introduce a national flag.
One of the most popular uses of a flag is to symbolize a nation or country. Some national flags have been particularly inspirational to other nations, countries, or subnational entities in the design of their own flags. Some prominent examples include:
* The flag of Denmark is the oldest state flag still in use (dates back to the 13th century). This flag, called the Dannebrog, inspired the cross design of the other Nordic countries: Norway, Sweden, Finland, Iceland, and regional Scandinavian flags for the Faroe Islands, Åland, Scania and Bornholm, as well as flags for the non-Scandinavian Shetland and Orkney.
* The Tricolour of the Netherlands is the oldest tricolor, first appearing in 1572 as the Prince's Flag in orange–white–blue. Soon the more famous red–white–blue began appearing—it is however unknown why, though many stories are known. After 1630 the red–white–blue was the most commonly seen flag. The Dutch Tricolor has inspired many flags but most notably those of Russia, New York City, and South Africa (the 1928–94 flag).
* The national flag of France, the Tricolore was designed in 1794. As a forerunner of revolution, France's tricolour flag style has been adopted by other nations. Examples: Italy, Costa Rica, Dominican Republic, Ireland, Haiti, Romania, Mexico, etc.
* The flag of Russia, the source for the Pan-Slavic colors red, white and blue, adopted by many Slavic states and peoples as their symbols. Examples: Slovakia, Serbia, Croatia, and Slovenia.
* The Union Flag (Union Jack) of the United Kingdom is the most commonly used. British colonies typically flew a flag based on one of the ensigns based on this flag, and many former colonies have retained the design to acknowledge their cultural history. Examples: Australia, Fiji, New Zealand, Tuvalu, and also the Canadian provinces of Manitoba, Ontario and British Columbia, and the American state of Hawaii; see commons:Flags based on British ensigns.
* The flag of the United States, also nicknamed The Stars and Stripes or Old Glory. In the same way that nations looked to France for inspiration, many countries were also inspired by the American Revolution, which they felt was symbolized in this flag. Examples: Liberia, Chile, Malaysia, Uruguay, and the French region of Brittany.
* The original tricolor Flag of Iran, the source for the Pan-Iranian colors Green, White and Red adopted by many Indo-Iranian or Aryan states and peoples as their symbols. Examples: Tajikistan, Kurdistan, Republic of Ararat, Talysh-Mughan.
* Ethiopia was seen as a model by emerging African states of the 1950s and 1960s, as it was one of the oldest independent states in Africa. Accordingly, its flag became the source of the Pan-African colors, or "Rasta colors". Examples: Togo, Senegal, Ghana, Mali.
* The flag of Turkey, which is very similar to last flag of the old Ottoman Empire, has been an inspiration for the flag designs of many other Muslim nations. During the time of the Ottomans the crescent began to be associated with Islam and this is reflected on the flags of Algeria, Azerbaijan, Comoros, Malaysia, Mauritania, Pakistan and of Tunisia.
* The Pan-Arab colors, green, white, red and black, are derived from the flag of the Great Arab Revolt as seen on the flags of Jordan, Kuwait, Sudan, Syria, the United Arab Emirates, Western Sahara, Egypt, Iraq, Yemen and Palestine.
* The Soviet flag, with its golden symbols of the hammer and sickle on a red field, was an inspiration to flags of other communist states, such as East Germany, People's Republic of China, Vietnam, Angola, Afghanistan and Mozambique.
* The flag of Venezuela, created by Francisco de Miranda to represent the independence movement in Venezuela that later gave birth to the "Gran Colombia", inspired the flags of Colombia and Ecuador, both sharing three bands of yellow, blue and red with the flag of Venezuela.
* The flag of Argentina, created by Manuel Belgrano during the war of independence, was the inspiration for the United Provinces of Central America's flag, which in turn was the origin for the flags of Guatemala, Honduras, El Salvador, and Nicaragua.
National flag designs are often used to signify nationality in other forms, such as flag patches.
A flag is a piece of cloth, often flown from a pole or mast, generally used symbolically for signalling or identification. It is most commonly used to symbolize a country. The term flag is also used to refer to the graphic design employed by a flag, or to its depiction in another medium.
The first flags were used to assist military coordination on battlefields, and flags have since evolved into a general tool for rudimentary signalling and identification, especially in environments where communication is similarly challenging (such as the maritime environment where semaphore is used). National flags are potent patriotic symbols with varied wide-ranging interpretations, often including strong military associations due to their original and ongoing military uses. Flags are also used in messaging, advertising, or for other decorative purposes. The study of flags is known as vexillology, from the Latin vexillum meaning flag or banner. (Wikipedia)