As a lieutenant-colonel, Lecourbe took part in the capture of Porrentruy in April 1792,[1] and later served in the armies of the Rhine and of the North, distinguishing himself at the Battle of Fleurus in 1794.
[1] He fought against Alexander Suvorov in Switzerland, where his actions at the Battle of Gotthard Pass delayed the Russian advance and contributed to the French victory at Zürich.
The count of Artois recalled Lecourbe to active duty in February 1815 and made him inspector-general of the 6th military Division with headquarters in Besançon.
He opposed Ney's eventual decision to switch sides complaining of personal affronts to his honour in being removed from command.
With an army of only 8,000 he held the city of Belfort for 15 days against the 40,000 Austrian troops of General Colloredo-Mansfeld, only agreeing a ceasefire on 11 July 1815, a feat which earned him a place of honour in French schoolbooks.