According to Merriam-Webster.com: “A flag is usually a piece of fabric with a distinctive design that is usually rectangular and used as a symbol, as a signaling device, or decoration.” In modern times a flag is usually associated with a political entity such as a country, state, or even a city. However, other organization may also have a flag as a symbol, such as political parties and religions.
Flags also are closely associated with the military. Many military units have guidons, or flags designed to represent the unit at ceremonies or in a formation. Officers that achieve the rank of General or Admiral are sometimes referred to as flag officers because they actually have flags that are usually flown when the officer is present on a military installation or on a ship.
According to Dr. Whitney Smith in “Flags through the Ages and Across the World”, primitive flags were likely just simple pieces of cloth perhaps dyed red in the blood of a slain enemy or animal and tied to wooden pole.
According to Livy the Romans used flags, or more properly vexilla, Latin for small sails, during the Second Punic War. A vexillum was a banner which hung from the famous Roman Legions’ eagle standards. It was gold on red and spelled out SPQR (Senatus Populus Que Romanus, Latin for Senate and People of Rome). The vexillum and standard was used to guide the legion into battle and was used to show a rallying place for the legionnaires after the battle.
Vegetius in his “De Re Militari” following Cichorius mentions that as early as the First Century AD the Dacians were using a dragon standard, which was adapted by the Romans by the Fourth Century AD. The dragon standard or draco, was a bronze dragon head with a piece of cloth similar to a windsock attached so when the air entered the dragon’s mouth the fabric part would inflate. Also the dragon’s head was designed to make a whistling or moaning sound as the wind moved through it to terrify the enemy.
“Ringrose’s Heraldry” states that by 1066 flags, or pennants, came to be flown from the tips of lances as heraldic devices, to allow a knight to be more easily identified. These pennants were each uniquely designed and dyed for each knight. In the later Middle Ages city-states and other political units started to use flags on the battlefield as well. These were later adapted for use as national emblems.
Norman Davies in “Europe a History” claims he oldest national flag still in use is the flag of Denmark or the Danneborg. The flag is a simple white cross on a red field. Legend places the use of the flag back to the 1200s AD. But the first record historical reference to the flag is from the 1500s.