In 1909, Crown Prince George killed his servant, and following a negative campaign in the press, he was compelled to give up his claim to the throne.

He later served with distinction in the army, was severely wounded during the First World War, and thereby became popular in the country, which aroused the alarm of his younger brother.

His grandfather, Alexander Karađorđević, had briefly ruled the Principality of Serbia during the period 1842–58, but he had been the first and only ruler from the family, which did not otherwise have a royal background.

The Prince had a reputation for being hot-tempered, and on one occasion attacked his tutor, Major Levasseur, who had to be dispatched back to Paris.

[citation needed] After the war the Karađorđević family was declared enemy-of-the-state by Josip Broz Tito's communist regime.

However, Prince George was permitted to retire in Belgrade as the only member of the royal family allowed to remain in the country.

While he was crown prince, George developed a close friendship with the mathematician Mihailo Petrović Alas, who had been retained to tutor him in mathematics.