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
After the Austro-Prussian War in 1866, the Prussian-dominated North German Confederation adopted a tricolour of black-white-red as its flag. This flag later became the flag of the German Empire, formed following the unification of Germany under the Prussian king who became emperor in 1871, and was used until 1918 with the end of the First World War. Black, white, and red were reintroduced as the German national colours with the establishment of Nazi Germany under Adolf Hitler in 1933, replacing German republican colours with imperial colours until the end of World War II.