Rubuta ci gaba don wannan sakin layi - Bayan aikinsa mara kyau a Roma a matsayin lauya da mai magana, ya shiga soja. Yaƙin farko da aka rubuta shi ne a ƙarƙashin Quintus Servilius Caepio kuma ya ƙare a Yaƙin Arausio a cikin 105 BC, inda ya nuna ƙarfin hali na musamman. Yin aiki a ƙarƙashin Gaius Marius, Sertorius ya yi nasara wajen leƙen asirin ƙabilun Jamusawa masu yawo waɗanda suka ci Caepio. Bayan wannan nasarar, kusan tabbas ya yi yaƙi a babban Yaƙin Aquae Sextiae
(yanzu Aix-en-Provence, Faransa) a cikin 102 BC wanda Teutones da Ambrones suka ci nasara. Wataƙila ya kuma yi yaƙi a Yaƙin Vercellae a 101 BC, inda aka ci Cimbri da nasara, wanda ya kawo ƙarshen mamayar Jamus. Bayan 'yan shekaru bayan yaƙe-yaƙe na Cimbric, mai kula da Sertorius Gaius Marius ya fadi daga alheri saboda goyon bayansa ga demagogue Lucius Appuleius Saturninus kuma shi da Sertorius dole ne su fita daga Rome na ɗan lokaci. Sertorius ya yi tafiya zuwa Hispania Ulterior kuma ya yi wa gwamnansa, Titus Didius, aiki a matsayin soja. Ya bambanta kansa ta hanyar sanya tawaye a cikin Castulo da kewaye da shi kuma an ba shi Grass Crown.