On 1 June, Charles de Gaulle was promoted brigadier general; on 5 June, Prime Minister Paul Reynaud appointed him Under Secretary of State for Defence, a junior post in the French cabinet. De Gaulle was known for his willingness to challenge accepted ideas; in 1912, he asked to be posted to Pétain's regiment, whose maxim 'Firepower kills' was then in stark contrast to the prevailing orthodoxy. He was also a long-time advocate of the modern armoured warfare ideas applied by the Wehrmacht, and commanded the 4th Armoured Division at the Battle of Montcornet. However, he was not personally popular; significantly, none of his immediate military subordinates joined him in 1940.