Publius Crassus
In the first year of the Gallic Wars, Caesar and his Celtic Aeduan allies fought a defensive campaign against the Celtic Helvetii, and waged an offensive against the Germanic Suebi and their allies, led by Ariovistus. During the decisive battle against the Suebi that brought the first year of fighting to its conclusion, Publius Crassus was given command of the cavalry. In 58 BC, Caesar's cavalry auxiliaries numbered 4,000, comprising regiments from the Aedui and from the Gallic nations of Gallia Transalpina, already a Roman province. In Caesar's army, the primary strategic applications of cavalry were reconnaissance and intelligence gathering, conducted by detachments of "exploratores" (“scouts”) and "speculatores" (“spies”); communications; patrols, including advance parties and guard units on the flanks of the army on the march; skirmishing, and securing the territory after fighting by preventing the flight of surviving enemy. The cavalry charge was infrequent. In the opening stage of the war against the Helvetii, Caesar had retained a Gallic command structure; a lack of strategic coordination, exacerbated by conflicting loyalties, led to poor performance, which Caesar sought to correct with a more centralized command. Publius Crassus is the first Roman named as a cavalry commander in the war, and was perhaps given the task of restructuring.