During World War II, he was held prisoner by the Nazis after refusing to take up the throne of the Axis forces' re-established Montenegrin puppet-state.

During the period of Yugoslav socialism, he was an active member of the Serb diaspora revolutionary organization and a diplomatic worker against the socialist government led by Marshal Tito.

[2] However, Danilo unexpectedly abdicated a few days later and his nephew the young Michael (who succeeded him as pretender) "reigned" as King Mihailo I under the guidance of a regent.

On 14 September 1929 the Regency of General Anto Gvozdenović ended and Mihailo renounced his dynasty's claim to the throne of Montenegro and declared allegiance to the Kingdom of Yugoslavia.

It was here that they were visited by Count Galeazzo Ciano and Joachim von Ribbentrop and were offered the throne of a new, independent Kingdom of Montenegro, but under Italian and German protection and guidance.

[citation needed] From its founding in 1946, Michael Petrovich spent his years as an active political dissident of the Communist regime and worked to bring about its downfall.

Michael married in Paris on 27 January 1941 Geneviève Denise Charlotte Prigent (4 December 1919, in Saint-Brieuc – 26 January 1990, in Lannion), second daughter of Dr. François Marie Prigent (Fontenay-sous-Bois, 8 March 1883 - Saint-Brieuc, 20 August 1947), a surgeon in Saint-Brieuc,[4][5] and wife (Neuilly-sur-Seine, 17 October 1905) Blanche Victorine Eugénie Bitte (Paris, 14 October 1883 - Saint-Brieuc, 3 December 1958), paternal granddaughter of Georges François Clair Prigent (Rospez, 2 April 1848 - Lannion, 29 August 1912) and wife Marie Françoise Kergus (Ploumilliau, 30 September 1857 - Lannion, 18 November 1897) and maternal granddaughter of Joseph Emile Bitte (Guermange, 22 February 1839 - Paris, 1 November 1896) and wife (Guermange, 17 June 1865) Marie Anne Victorine Renner (Guermange, 22 February 1843 - Paris, 26 July 1913).