The Ministry of Defence in the Netherlands is operating military systems like vehicles, aircraft, helicopters and ships all around the world. The operational conditions of these systems are demanding and vary continuously. To ensure their availability, a lot of maintenance is required, which must be optimized to match the available budgets. More accurate predictions of upcoming failures result in maintenance just-in-time, high availability and low costs. In my work I will focus on deriving quantitative relations between the operational use (and environment) of military systems and the associated degradation behavior.