<p>Human augmentation is defined as the use of science or technology to modify human performance temporarily, or permanently, to exceed normal physical and/or psychological capabilities of a human body. Our previous work proposed nine ethical principles of human augmentation in the defence context: necessity, human dignity, informed consent, transparency and accountability, equity, privacy, ongoing review, international law, and broader social impact. Here we describe the results of a mixed-methods study using focus groups (<i>N</i>_{<i>Groups</i>} = 9) and a web-based survey among serving military personnel (<i>N</i>_{<i>Participants</i>} = 43) examining how important and appropriate the participants thought the principles were when considering the development, adoption, and implementation of human augmentation technology. This study explores the participants’ stated reasons for their ratings, and the association with indicators of experience and socio-demographic groups. This work provides insights into how the principles can relate to each other at various stages of the technology life cycle, and how they could function together to support a thorough ethical analysis during the implementation of such technology. Following our analysis, several refinements to the principles are subsequently suggested.</p>