In The Song of Roland,the cause of war is somewhat ambiguous. We are told in the first stanza that Charlemagne has essentially conquered Spain, but are never told why (The Song of Roland 3). We are, however, repeatedly informed that the Saracen King “[does] not love God (The Song of Roland 3). There seems to be a moral and religious superiority in the warfare that regards conquering as the right and duty of the Christian French, which is not surprising given the time period that the poem was written in. This moral superiority is further asserted because the Saracens create a deceitful plot to get Charlemagne to leave Spain, which involves an embassy promising that they will surrender, and then collaborate with a traitor, Roland’s stepfather Ganaleon, to plan a secret ambush on Charlemagne’s armies (Wikipedia contributors). These dishonorable actions are presented by the author as sufficient justification for retaliation.

Figure 1. France and Spain with the Ebro River. Wikipedia contributors. "Ebro." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 17 Apr. 2012. Web. 23 Apr. 2012.
Though there may have been some religious impetus for the actual Battle of Roncesvalles, other factors motivated both sides, and Charlemagne’s reasons for getting involved “are not clear” because “the campaign is not treated very fully in contemporary sources” (Heer 106). The ambiguity in the poem is, therefore, not surprising. We do know that Suleiman, the Muslim governor of Barcelona, did go to Charlemagne’s court to enlist his help against a rival Muslim ruler and that he promised Charlemagne “all of Spain up to the river Ebro” in return for his services” (see Figure 1) making the completely moral nature of the King’s motivations in the poem seem unlikely (Heer 106).The campaign was ultimately unsucessful however, and the French eventually had to return to Spain.
As to the opposing side in the battle itself, the French were actually attacked at Roncesvalles by the Christian Basques because “the Franks destroyed the city [Pamplona] in an act of departing malice” on their way out of their largely unsuccessful campaign in Spain (Lewis 252). This made the Basques, who were not enthusiastic about the idea of being conquered by the Franks in any way despite their shared religion, furious, and motivated them to retaliate at Roncesvalles (Lewis 252-253).
Works Cited
Heer, Friedrich. Charlemagne and his World. New York: Macmillian Publishing Co., 1975. Print.
Lewis, David Levering. God’s Crucible: Islam and the Making of Europe, 570 – 1215. New York: W.W. Norton & Co. Inc., 2008. Print.
The Song of Roland. Trans. W.S. Merwin. New York: Modern Library, 2001. Print.
Wikipedia contributors. “The Song of Roland.” Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 23 Apr. 2012. Web. 23 Apr. 2012.