In 1870, during the Franco-Prussian War, the South German states joined the North German Confederation. The new constitution of January 1st, 1871, renamed the country from 'North German Confederation' to 'German Empire'. The holder of the "Bundespräsidium" received the additional title of an Emperor. The political system as described in the constitution, and the flag, remained the same. (The final constitution of the Empire stems from April/May 1871; as a result, nearly all terms that included 'federal' were changed to 'imperial'.)