After the outbreak of the Napoleonic Wars and creation of the Duchy of Warsaw, in 1808, Joanna Żubr with her husband Michał Żubr defected from Austrian-ruled Volhynia. Both joined the army, with Joanna initially serving as a camp-follower. However, soon she joined the 2nd Infantry Regiment (4th company, 2nd battalion) as a private, hiding that she was a woman from both her superiors and fellow soldiers. In 1809 she took part in the Galician Campaign and distinguished herself in the Battle of Zamość of May 19 of that year. For her bravery she was awarded with the Virtuti Militari medal by Prince Józef Poniatowski. She was the first female soldier to be awarded with this prestigious decoration and one of the first women in the world to receive a military award for bravery in battle.
After the campaign she joined the 17th Infantry Regiment in the Dąbrowski's Division under Jan Henryk Dąbrowski. Her husband was an ensign in the same unit and Joanna Żubr was promoted to sergeant, as the first woman in the Polish Army. Their unit, renamed to Greater Polish Division, took part in the Napoleon's invasion of Russia and the campaign in Belarus.
During the fights and Napoleon's retreat, she got separated from her division, but she managed to escape from Russia on her own. In the summer of 1813, weeks after Prince Józef Poniatowski's forces had abandoned Kraków, she reached the Polish units in Saxony and served with distinction until the Treaty of Fontainebleau and the end of the war.
Together with her husband, she returned to Poland. Since she could return to neither Austrian-occupied nor Russian-held parts of Poland, they settled in Wieluń. She died there in 1852 during a cholera epidemic, at the age of approximately 80.
- Encyklopedia Wojen Napoleońskich - R. Bielecki ("Encyclopedia of the Napoleonic Wars" in Polish)
- List of recipients of the Order Virtuti Militari