The text providing the basis of this article has so far never been connected with Leonardo’s Battle of Anghiari. It shows how a Florentine humanist scholar, Piero Vettori, understood this masterpiece in the middle of the sixteenth century, and from it threads develop leading to a better understanding of both its grandiose composition, and eventually, its inglorious end. It is suggested that Leonardo’s Battle of Anghiari was conceived of and intended to be executed as a ‘Greek’ painting in Florence, ‘the new Athens’, and precisely for this very reason deteriorated so quickly.