Flag of Prussia
The state of Prussia had its origins in the separate lands of the Margraviate of Brandenburg and the Duchy of Prussia. The Margraviate of Brandenburg developed from the medieval Northern March of the Holy Roman Empire, passing to the House of Hohenzollern in 1415. The Duchy of Prussia was created in 1525 when the eastern lands of the Teutonic Knights were secularized as Polish fief by Albert of Brandenburg-Ansbach, a member of a cadet branch of the Hohenzollerns. Prince-elector George William inherited the Duchy of Prussia in 1618, uniting Brandenburg and Prussia under one ruler; the elector's state became known as Brandenburg-Prussia. The Kingdom of Prussia was created when Elector Frederick III assumed the title of Frederick I, King in Prussia, on 18 January 1701.
Prussia ceased to be a kingdom after the fall of the German Empire resulting from World War I, becoming instead the Free State of Prussia. The state of Prussia was abolished in 1947 following World War II.
The Prussian national and merchant flag was originally a simple black-white-black flag issued on May 22, 1818, but this was replaced on March 12, 1823 with a new flag. The revised one (3:5) was parted black, white, and black (1:4:1), showing in the white stripe the eagle with a blue orb bound in gold and a scepter ending in another eagle. On its breast were the intertwined initials 'FR' for 'Fridericus Rex'. The axis of the eagle is at 2/5 of the flag's total length.
The Prussian war flag (3:5), adopted November 28, 1816, was originally swallowtailed for one fifth of the total length; the tail was later abandoned. At two fifths it showed the Prussian eagle (two thirds of the flag's height). In the canton the Iron Cross was placed (one third of the flag's height).
The Iron Cross was established in 1813 during the war against Napoleon I as a decoration for courageous common soldiers. It was renewed in the Franco-Prussian War of 1870 and in World War I. It also appeared in the canton of the war flag of the German Empire.
The royal standard of Prussia showed the Iron Cross charged with the shield and crown of the small state arms surrounded by the collar of the Order of the Black Eagle. On the blades of the cross is the motto Gott mit uns. Between the arms were Prussian eagles along the edges and a royal crown in carré with them, all on a purple or red background.
After the German Revolution of 1918–1919, the Prussian state was slow to adapt its heraldry to republican forms. Only July 11, 1921 new arms were decreed by the Prussian prime minister. The 'gothic' eagle made way for the more natural-looking flying one and lost all its garments.
On December 12, 1921, the Ministry of State decreed that the Prussian flag was to be only black and white.
On February 24 and April 23, 1922, the ministry issued a service flag similar to the national flag of the 19th century - black borders above and below, being 1/6 of the total height of the flag, with the new eagle.
The Germany national football team home dress has always been a white jersey and black shorts, the colors of the Prussian flag.
See also 
- Source: H.G. Ströhl, Deutsche Wappenrolle, Stuttgart 1987
- Siebmacher, Grosses Wappenbuch, Band I, 1 Abteilung, 5. Teil, Nuremberg, 1929