 According to Professor Mamadou Diouf and Profssor Mara Leichtman (2009), the Serer Saafi were also purely egalitarian and rejected all forms of centralised government, the caste system, Islam and slavery.Conflicts erupted with the Muslims to the north, as when Marabout Nasr al Din attacked Mauritania and the Wolof across the border in 1673, but he was defeated through an alliance between local forces and the French.During the Napoleonic Wars, Great Britain captured Gorée in 1803 and Saint-Louis in 1809, and proclaimed the abolition of the slave trade in 1807, to which the French had to agree upon recovering the two posts.