This study provides an overview of the strong military component of Celtiberian society, dating back to the sixth century BC and manifesting itself especially during the wars against Rome in the second century BC. This bellicose character developed as a result of a long tradition of warrior-shepherds who formed part of the Bronze Age "proto-Celtic" substrate. From the first millennium BC on, Celtiberian society became increasingly hierarchical and by the Iron Age warrior elites had emerged that subsequently evolved into hereditary regional clans. Archaeology, especially the excavation of cemeteries dating from the sixth to the first centuries BC, has provided most of our information about the Celtiberian warrior aristocracy, referred to in later literary sources as nobles and princes. The arrival of the Carthaginians and Romans ushers in the appearance of oppida as administrative centres that controlled large territories and provided cohesion in the wars against Rome. Within this framework, equestrian structures - the equites - emerged with training strategies that influenced military tactics. Graeco-Latin sources refer to Celtiberian customs such as single combat conflict between champion-warriors and Celtiberian warriors as mercenaries. Epigraphic sources, on the other hand, document the existence of institutions such as magistrates, supra-family organisational structures, and hospitality pacts. In this society, warlike, virile and agonistic ideals played an essential role. Thus, analysis of different kinds of evidence (literary sources, iconography, and funeral practices) provides information about the existence of highly religious ritual practices linked to war. This is verified by the fact that the gods were invoked in such rituals and were called upon to witness pacts. Customs such as the devotio, which had strong ritual associations, must have been relatively frequent among the Celtiberians. Finally, information is included about fighting methods and the concept of war, which in the Hispano-Celtic world evolved along with society, as is confirmed by important variations documented over five centuries of Celtiberian development.