Early life and military career
The future king and emperor was born William Frederick Louis of Prussia (Wilhelm Friedrich Ludwig von Preußen) in the
Berlin on 22 March 1797. As the second son of
Louise of Mecklenburg-Strelitz and
Prince Frederick William, himself son of King
Frederick William II, William was not expected to ascend to the throne. His grandfather died the year he was born, at age 53, in 1797, and his father Frederick William III became king. He was educated from 1801 to 1809 by
Johann Friedrich Gottlieb Delbrück , who was also in charge of the education of William's brother, the Crown Prince
Frederick William. At age twelve, his father appointed him an officer in the Prussian army.
William served in the army from 1814 onward. Like his father he fought against
Napoleon I of France during the part of the
Napoleonic Wars known in Germany as the Befreiungskriege ("Wars of Liberation", otherwise known as the
War of the Sixth Coalition), and was reportedly a very brave soldier. He was made a captain (Hauptmann) and won the
Iron Cross for his actions at
Bar-sur-Aube. The war and the fight against France left a lifelong impression on him, and he had a long-standing antipathy towards the French.
In 1815, William was promoted to major and commanded a battalion of the 1. Garderegiment. He fought under
Gebhard Leberecht von Blücher at the Battles of
He became a diplomat, engaging in diplomatic missions after 1815.
In 1816, William became the commander of the Stettiner Gardelandwehrbataillon and in 1818 was promoted to Generalmajor. The next year, William was appointed inspector of the
VIII. Army Corps. This made him a spokesman of the Prussian Army within the
House of Hohenzollern. He argued in favour of a strong, well-trained and well-equipped army. In 1820, William became commander of the 1. Gardedivision and in 1825 was promoted to commanding general of the
III. Army Corps.
In 1829, William married Princess
Augusta von Sachsen-Weimar-Eisenach after Princess
Elisa Radziwill, his cousin whom he had been attracted to, was deemed an inappropriate match by his father. William had been forced to abandon the relationship with Elisa in 1826. Augusta was the daughter of Grand Duke
Karl Friedrich von Sachsen-Weimar-Eisenach. Their marriage was outwardly stable, but not a very happy one.
In 1840 his older brother became King of Prussia. Since he had no children, William was first in line to succeed him to the throne and thus was given the title Prinz von Preußen.
 Against his convictions but out of loyalty towards his brother, in 1847 William signed the bill setting up a Prussian parliament (Vereinigter Landtag) and took a seat in the upper chamber, the Herrenhaus.
Revolutions of 1848, William successfully crushed a revolt in Berlin that was aimed at his elder brother, King Frederick William IV. The use of cannon made him unpopular at the time and earned him the nickname Kartätschenprinz (Prince of
Grapeshot). Indeed, he had to flee to England for a while, disguised as a merchant. He returned and helped to put down an uprising in
Baden, where he commanded the Prussian army. In October 1849, he became governor-general of
Westfalia, with a seat at the Kurfürstliches Schloss in
During their time at Koblenz, William and his wife entertained liberal scholars like the historian
Maximilian Wolfgang Duncker or
August von Bethmann-Hollweg and
Clemens Theodor Perthes . William's opposition to liberal ideas gradually softened.
In 1854, the prince was raised to the rank of a field-marshal and made governor of the
fortress of Mainz.
 In 1857 Frederick William IV suffered a
stroke and became mentally disabled for the rest of his life. In January 1858, William became
Prince Regent for his brother, initially only temporarily but after October on a permanent basis. Against the advice of his brother, William swore an oath of office on the Prussian constitution and promised to preserve it "solid and inviolable". William appointed a liberal,
Karl Anton von Hohenzollern-Sigmaringen as Minister President and thus initiated what became known as the "New Era" in Prussia, although there were conflicts between William and the liberal majority in the
Landtag on matters of reforming the armed forces.