Born in the Lorraine, François Nicolas Benoît Haxo WAS originally from Lunéville ( Meurthe-et-Moselle ). He became a captain at 22 years old, taking part in the campaigns of 1794 and 1795 in the armies of the Republic. In 1796, he was a student at the brand new Ecole Polytechnique, founded two years earlier. As an engineer he carried out fortification work along the borders. Under the first empire, in 1810 he was in charge of work at the fort of Bard (in the Jura ) and then of the fortifications in Italy, followed by others for improving the defence of the Dardanelles strait in Turkey. In 1811 Napoleon appointed him as head of the army's engineering corps in Germany, where he carried out major works in Meldin and in Dantzig, where he constructed the casemated batteries. As governor of the place de Magdebourg and then head of engineering in the Imperial Guard in 1813, his career did not end with the fall of the Empire as, during the Restoration, he carried out the duties of inspector general of the fortifications. For many years, he worked on the border fortifications, restoring the fortresses that were essential for the defence of the kingdom.