Unlike Vauban, de Cortmontaigne never commanded a siege and was a relatively junior official for much of his career, only reaching the rank of Maréchal de Camp in 1748. Although viewed as a competent engineer, his prominence has been attributed to the ability to write clear and concise memoranda, with a wealth of detail; during a debate in 1741 with Forest de Bélidor over upgrades to the defences of Metz and Neuf-Brisach, he 'proved' his designs superior, using calculations he claimed were based on Vauban's principles. As the Marquis de Montalembert remarked after the unsuccessful 1779-1783 Siege Gibraltar, using the same approach he could 'prove' Gibraltar should have been taken after six days.