Flag of Germany
When Heinrich XI, Prince Reuss of Greiz was appointed by Joseph II, Holy Roman Emperor to rule the then-new Principality of Reuss-Greiz on 12 May 1778, the flag adopted by the "Fürstentum Reuß-Greiz" was the first-ever appearance of the black-red-gold tricolour in its modern arrangement in any sovereign state within what today comprises Germany – the Reuss elder line that ruled the principality used a flag whose proportions were close to a "nearly square"-shape 4:5 hoist/fly ratio, instead of the modern German flag's 3:5 figure.
Flag of Germany
Two other states that were created after the war, Rhineland-Palatinate (French zone) and Lower Saxony (British zone), chose to use the black-red-gold tricolour as their flag, defaced with the state's coat of arms. These two states were formed from parts of other states, and no colour combinations from these previous states were accepted as a new state flag. This led to the use of the black-red-gold for two reasons: the colours did not relate particularly to any one of the previous states, and using the old flag from the Weimar Republic was intended to be a symbol of the new democracy.