This chapter examines highly automated and autonomous weapon systems from an engineering standpoint, covering technology evolution, defence engineering processes, and economic pressures. It shows that a system engineering approach with functional partitioning and specifications offers a way to assess the lawfulness of a chain of decisions for an autonomous system in the same way as is carried out for human operators. The chapter suggests that the increased level of automation for peaceful purposes. The defence engineering community addressed the problem of differentiating between automation and autonomy by developing the concept of autonomy levels. Interpretation of the automation spectrum as a continuum of weapon control systems does not follow; the spectrum is for the individual control subsystems which together make up the whole weapon control system. Life extension programmes include processing upgrades and increased levels of automation to enable the military user to operate in an increasingly complex environment.