The Prussian Kingdom was the most powerful country in the Confederation of the Rhine, and was receiving fully Austrian and French support. Since then the Prussians, commanded by Bismarck iron hand, attacked south Denmark and the old Polish Kingdom.
The Great World War
The Empire was able to force the Doge's family in Austria to turn against them. At the start, Italy was neutral so the Germanic Pact was winning all battles on all fronts. Italy was invited to join the Germanic Pact, but refused it because of the French, that made possible the Austrian/Russian/French/Italian alliance. When the Italians entered in the Latin Alliance the war was over. The Italians were able to convince almost the whole world to enter against the Germanic Pact. At the start the Austrian front was lost, since the Austrians were reconquer by the combined Ottoman-Italian forces. The Germans were alone. They tried to settle an treaty to stop the war to made able the survive of the German Empire. After it, Germany was able to hold many of the territories conquer, to avoid an new war.
Right after the treaty, several Reichstag parliamentaries approved the Republican Act, that ordered the Kaiser execution and an new republican constitution, because of the German "defeat". As soon the Kaiser heard that, he ordered to the army, that fully supported him, to arrest the whole Reichstag parliamentaries. After that, never were heard again in Germany the word "Republic"
New German Empire
After the "republican" experience, the German Empire completely changed the Flag, Coat of Arms, and Anthem. The Empire was the major nation in central Europe, controlling almost everybody.
As the German Empire demilitarized, as order of the Peace League, the Polish were ascending, and of course, the Germans asked help to the league, that granted. Right after none a single nation recognized Poland as free of Germany.