A key goal in safety-critical system development is to provide assurance that the critical requirements are sufficiently addressed. This goal is typically refined into three sub-goals, namely that the safety requirements are validated, satisfied and traceable. The achievement of these sub-goals is typically communicated by means of a safety argument supported by items of evidence (e.g. testing, review or analysis). In this paper, we explore the relationships between goals, requirements, and arguments. We discuss how argumentation is used to assure the decomposition and traceability of requirements in safety-critical applications. Particularly, we focus on the achievement of goals related to both the requirements artefacts and the underlying requirements process.