Junot was born in Bussy-le-Grand and studied in Chatillon. He was studying in Paris when the French Revolution began and joined the volunteer army. He met Napoleon at the siege of Toulon in 1793 when he was a sergeant and he became Napoleon's aide. His career rose with that of Napoleon - he fought in Italy, Egypt (1798-1801), Austria (1805), the Peninsular War (1807), and Russia (1812).
He distinguished himself in Italy but received a serious head wound at Lonato, which some claim led to a permanent change in his thinking and character -reduced the quality of his judgement and made him rash and temperamental. He was made a minor general for the Egyptian campaign but was injured in a duel and captured when he was returning as an invalid to France. When he was returned he was promoted and made commander of Paris, although his failure to be made a marshal dismayed him. He married Laure Permon at this time. He was briefly ambassador to Portugal before hurrying back to serve under Napoleon at the Battle of Austerlitz (December 2, 1805). After that he returned to Paris.
Junot's major command was during the Peninsular War. He commanded the invasion of Portugal in 1807, setting out in November from Salamanca he captured Lisbon in early December and was made Duke of Abrantes and governor of Portugal. But when the British arrived in August 1808, the French were beaten at Vimeiro (August 21) and Junot was almost cut-off; only the signing of the advantageous Convention of Sintra allowed him to avoid capture, and he returned to France in October, narrowly escaping a court martial. He returned to the Iberian peninsula in 1810 as part of the army under Andre Massena and was badly wounded.
In the Russian campaign Junot's record was erratic; he was blamed for allowing the Russian army to retreat following the Battle of Smolensk (August 17), but at the Battle of Borodino (September 7, 1812) he commanded the 8th Corps competently.