Eleonore's father was an officer in the Prussian guards, on a low income. She grew up poor and was sent by her father to the military orphanage in Potsdam when her mother died. There she later found work as a domestic servant, though she was also interested in the war against Napoleon from an early age.
During these wars she disguised herself as a man and registered for 1 Jägerbataillon of the Lützow Free Corps under the name August Renz, serving first as a drummer, then later as an infantryman. She was heavily wounded at the Battle of the Göhrde and field-surgeons, rushing to treat her wounds, discovered she was a woman and took her to Dannenberg, where she succumbed to her wounds three weeks later.
In retrospect, she was strongly idealized as a chaste heroine and honoured as "Potsdam's Joan of Arc" ("die Potsdamer Jeanne d'Arc"). Various plays and poems were written on her life (including one by Friedrich Rückert), whilst Ludwig van Beethoven began a "Bühnenmusik" (WoO 96) on her, with a libretto entitled "Eleonore Prochaska" written by the Prussian royal private-secretary Friedrich Duncker.
In 1863, a commemorative marker was erected over her grave at St.-Annen-Friedhof in Danneburg and in 1889 her home town of Potsdam created a monument to her memory ("Der Heldenjungfrau zum Gedächtnis", or "In memory of the virgin-heroine"), which still survives in the almost completely cleared Alten Friedhof (old cemetery).
Eleonore was one of many German women to fight in the Napoleonic Wars, though almost all of them were ejected from the army when it was found out that they were women.
The only known example was Friederike Krüger (1789–1848), who (thanks to the protection of her brigade commander) became the only known female corporal in the Prussian army. Finally she served in 2nd Garde-Regiment zu Fuß. Her request to retire was accepted in 1816 and she returned to civilian life.