La Marseillaise was written in 1792 by Claude Joseph Rouget de Lisle in Strasbourg after the declaration of war by France against Austria, and was originally titled "Chant de guerre pour l'Armée du Rhin". The Marseillaise was a revolutionary song, an anthem to freedom, a patriotic call to mobilize all the citizens and an exhortation to fight against the tyranny and the foreign invasion. The French National Convention adopted it as the Republic's anthem in 1795.
Here is a piano duet 4 hands arrangement, 4 pages (2 pages both hands, 1 page prima, 1 page seconda) with downloadable mp3s just for audio help.