He decided upon a military career, and served in the regiment of Medoc from 1784 to 1787, when, having no hope of promotion on account of his non-noble birth, he retired with the rank of sergeant.

His gallant defense of the little fort of Bitsch in the Vosges in 1792 drew attention to him; he was transferred to the regular army in November 1793, and after serving in numerous actions on the Belgian frontier he was promoted general of brigade, in June 1794 for his conduct at the Battle of Kaiserslautern.

He was André Masséna's right hand all through the Swiss campaign of 1799, first as a general of division, then as chief of staff, and won extraordinary distinction at the Second Battle of Zurich.

He took a leading role in the War of the Third Coalition, commanding the famous division of "grenadiers Oudinot," made up of hand-picked troops and organised by him, with which he seized the Vienna bridges, received a wound at the Battle of Schöngrabern in Lower Austria against the Russians.

He was made a titular duke in chief of the duché-grand fief of Reggio in the satellite Kingdom of Naples, and received a large money grant in April 1810.

[1] From 1810 to 1812 Oudinot administered the government of the former Kingdom of Holland, and commanded the II Corps of La Grande Armée in the Russian campaign.