Friedrich Karl was born at the Royal Palace in Berlin on 20 March 1828, as the only son of Prince Charles of Prussia, the brother of future German emperor William I.

[1] He became a member of the Corps Borussia Bonn in 1847 and was awarded Prussia's Lifesaving Medal for rescuing a child from the Rhine the same year.

His company was issued the breech-loading Dreyse needle gun and the Prince produced an article on its probable future impact, writing that the troops could be prevented from firing off all their ammunition through good training and discipline.

In 1851, the Prince wrote a radical field manual for light troops, underlining the importance of training individual soldiers to take the initiative and not wait for orders.

During the following peace years he was promoted to colonel in 1852 and granted the command of the Guards Dragoon Regiment, where he introduced realistic field exercises and insisted on combat readiness.

In 1860, the Prince published a military book, titled, "Eine militärische Denkschrift von P. F. K.", which contained a series of reform proposals.

Promoted to General der Kavallerie, the Prince took part in the Second Schleswig War of 1864 against Denmark, where he held command over the Prussian troops in the Austro-Prussian expeditionary force and defeated the Danes at the Battle of Dybbøl.

The 3rd Division was victorious in the resulting Battle of Gitschin but the campaign was ill regarded by the headquarters as it was outside of the strategic plans of King William of Prussia.

[4] Chief of Staff Helmuth von Moltke inferred that the operational aim of Friedrich Karl was not to unite with the Second Army at Jičín but to capture Prague on his own.

On 29 November 1854 at Dessau he married Princess Maria Anna of Anhalt-Dessau (1837–1906), daughter of Leopold IV, Duke of Anhalt.