Plateau first entered politics in 1908 when he began selling the Revue d'Action Française newspaper, only a few weeks following its inception.

[1] Marius Plateau served as a sergeant during World War I, receiving a commendation for "exemplary courage" stating:[1] "Vaillant non-commissioned officer, on 20 September 1914, attacking the position of Port-Fontenoy, all the officers of the company having fallen, [he] burst onto a glacis beaten by extremely violent machine-gun fire, to create a diversion and attract the attention of the enemy.

[1][2][3] On 22 January 1923 Germaine Berton, a French anarchist, shot and killed Plateau with a revolver at the Action Francaise headquarters.

Berton declared at her trial, "I considered Daudet and Maurras responsible for the occupation of the Ruhr" for her reason for the assassination.

[8] Action Française claimed the assassination was part of a larger "German–Bolshevist" plot and called for the mobilization of Camelots du Roi.

[10] In Revue d'Action Française, Robert Havard de La Montagne stated that "certain acts of violence are necessary and noble".

[10] The assassination led to an increased solidarity within Action Française, with Jacques Maritain writing to Charles Maurras: "The idea of the dangers you are running makes even dearer to the hearts of all those who love France and intelligence".