German troops after surrendering to the U.S. Third Army carry the white flag (WW2 photo).
A white flag is an international sign of either surrender, or truce, i.e., of peaceful intent, typically in time of war. Soldiers carrying or waving a white flag are not to be fired upon, nor are they allowed to open fire. A white flag signifies to all that an approaching negotiator is unarmed, and an intent to surrender or a desire to communicate.
Persons carrying a white flag are expected to maintain neutrality, and may not engage in warlike acts. The improper use of a white flag is a forbidden ruse of war and constitutes a war crime of perfidy. There were several reports of insurgent fighters using white flags as a ruse to approach and attack U.S. and Coalition forces during the early days of Operation Iraqi Freedom in early 2003.
The royal standard of France was once a plain white flag (to which a fleur-de-lys was later added, and which was replaced by the Tricolor). An unadorned white flag was also the standard of the Stewards of Gondor in the Middle-earth legendarium of author J.R.R. Tolkien. In Buddhist countries, white is the colour of mourning, so a white flag is used where other cultures might fly a black flag.
Hoisted at the mainmast of a man-of-war it is the flag of an admiral of the fleet.
The man-of-war flag is precisely similar to that of the mercantile marine, except that in the case of the former the shield of Savoy is surmounted by a crown.
The Persian flag is white with a border, green on the upper edge of the flag and in the fly, and red in the hoist and on the lower edge.