General Humbert returned to France in a prisoner exchange. He would serve with the Armies of Mayence, Danube and Helvetia. Then he embarked for Saint Domingo and participated in several Caribbean campaigns. There it was rumored that he had an affair with Pauline Bonaparte, wife of his commanding officer Charles Leclerc. Humbert was returned to France by order of General Leclerc in October 1802, for "prevarications, and liaison relationships with organizers of the inhabitants and with leaders of brigands."
As a committed republican, Humbert was unhappy at Napoleon's Imperial pretensions and especially his coronation as Emperor in 1804. Humbert was in fact dismissed from the army in 1803, at first retiring to Morbihan in Brittany. In 1808 he emigrated to the now American city of New Orleans, in Louisiana, home to a growing French community including other veterans and refugees from Napoleon’s France. Once there, Humbert reportedly made the acquaintance of pirate Jean Lafitte. In 1813 he joined in an unsuccessful rebellion against Spanish rule in Mexico.
Meanwhile, the United States found itself at war again with Great Britain, as in 1812 it objected to repeated mistreatment of both the American nation and its citizens at British hands.
In the second year of that war, the British resolved to focus on to New Orleans having already heavily ravaged Atlantic Coast of the United States. Lieutenant-General Sir Edward Pakenham agreed to replace General Robert Ross as commander of the British North American army after Ross was killed on September 12 during skirmishing prior to the Battle of North Point near Baltimore.
Meanwhile, Andrew Jackson, now a Major General campaigning in Florida against both the Spanish and Indians, wasnotifying Washington of the growing British threat. Stopping to fortify Mobile, Alabama, Jackson moved to meet the anticipated British invasion. By December 1, Major General Andrew Jackson reached New Orleans with less than 2,000 men but the promise of a total final force of more than 12,000 to counter the roughly 6,000 British – almost all veterans of Wellington’s victorious Peninsular Army. Roughly a week later, on December 8, the British reached the region. .
Augmenting Jackson’s small army from New Orleans were a battalion of free Blacks, a battalion of New Orleans Volunteers, and a few veterans of Napoleon’s army including Humbert. Jackson welcomed the French veteran but found that his American troops resisted having him as a commander. Reportedly some of the American troops complained that they couldn’t understand the veteran French general! Humbert became aide, advisor, and an extra pair of eyes.
One moment that illustrated the challenges faced by Humbert and Jackson was when Jackson directed General Humbert to cross the Mississippi River and retake a lost American position. Humbert, in his old uniform, was delighted to accept the assignment. But since Jackson neglected to give him written authority, American officers on the west bank refused to take orders from a man who was not a citizen, and Humbert returned angrily to Jackson's Headquarters.
General Pakenham was having an even more frustrating day. As he rallied his troops near the main American position, grapeshot from US artillery shattered his left knee and killed his horse. As he was helped to his feet by his senior aide-de-camp, Major Duncan MacDougall, Pakenham was wounded a second time in his right arm. With MacDougall’s assistance, Pakenham mounted MacDougall's horse and yet more grapeshot ripped through his spine. Fatally wounded, he died as he was being carried off the battlefield on a stretcher at the age of 36. His last words were reputed to be telling MacDougall to find General Lambert to tell him to assume command as well as "Tell him... tell Lambert to send forward the reserves." Ironically, MacDougall had performed similar service the Pakenham’s predecessor General Ross when he was fatally wounded the previous year. The battle ended in defeat for the British.
The reality unknown to everyone in New Orleans was that a general ceasefire for the war had already been declared by the Treaty of Ghent, signed in the city of Ghent in Belgium on 24 December 1814, though a formal peace would wait until the Treaty was ratified in Washington and London. The news of the treaty signing only reached New Orleans in February.
The victorious American commander, Major General Andrew Jackson (March 15, 1767 – June 8, 1845), would go onto become the 7th President of the United States. He would eventually retire from public life and return to his home, the Hermitage, in Nashville, Tennessee where he is buried.
General Jean Joseph Amable Humbert (22 August 1767 – 3 January 1823) spent his final years in New Orleans, though reportedly not without one more adventure in Buenos Aires alongside rebels there. Again in New Orleans he was a schoolteacher and somewhat of a local celebrity, appearing from time to time in his old French military uniform and under possibly under the influence. The General is buried in St. Louis Cemetery #1.
After the death of General Pakenham (19 March 1778 – 8 January 1815), his body was recovered from the battlefield and returned home in a cask of rum. The Honourable Sir Edward Pakenham GCB is buried in the Pakenham family vault in Killucan, Co Westmeath, Ireland.