The story of the siege of Lisbon

The story of the Siege of Lisbon written by José Saramago ... There was a manuscript, and the manuscript talked about Islamic Lisbon, and about the Portuguese siege of it. The adhan was being called in "Lisbon" and the Portuguese forces were preparing to expel the Muslims from it. The hero is a proofreader named "Raymondo Silva", his heroism lies in that he does not like history in its current form, and for this he decides to add a slight modification to this manuscript: he will change one word in the manuscript, which is the word "yes" and replace it with "no". How will the history be after this slight modification? Does it change much?