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After a brutal winter, fighting commenced between the two opposing forces in the spring fighting season. The Battle for the Asio River (modern name, Esino) was the first battle of the season, taking place on the banks of the river. Fighting was bloody with the Optimate infantry advancing and successfully breaking the Populares infantry who were obliged to fall back. As this was happening, the Optimate cavalry commanded by Gnaeus Pompeius Magnus attacked the retreating Populares forces inflicting heavy casualties.