War shaped the existence of the Roman empire, determined its decline and conditioned the nature of post-Roman structures. The majority of wars were undertaken in response to external threats, serious ones in contrast to the excuses which were sometimes exploited during the Republic to justify expansionist campaigns. Most warfare had the predictable rhythms imposed by seasons and logistics. In the east Roman commanders could forecast when Arab tribes would be inactive because of religious celebrations. It was usually to the Romans' advantage to confirm the cessation of hostilities with a formal agreement. In the east written treaties became increasingly more specific during the fifth century. Warfare was preceded by careful preparations, not just of men and material but also of information, as appears from a tenth-century account which purports to describe Constantine's practice. The traditional Latin religion had significance in structuring the lives of Roman soldiers, which was particularly relevant in a unit largely recruited from eastern provincials.