This chapter provides a critical analysis of the material scope of NIAC and is divided into seven sections. The first explores the material concepts of NIAC pursuant to both CA3 and APII,  and explores how the drafters understood these  concept and how it has been interpreted in practice. Second, it examines the concept of NIAC contained in Additional Protocol II of 1977, looking at how its distinct identity emerged, as well as its specific material elements. The second section explores some of the legal and operational challenges that arise from the existence of two categories of NIAC, and in particular how the activation of APII can fragment the applicable legal regime, resulting in fluctuating levels of protection during NIAC. The fourth section undertakes a comparative analysis of the material scope and associated threshold of NIAC pursuant to the Tadić definition of NIAC (CA3) and that contained in APII, in order to identify areas of convergence and divergence. The fifth section explores how developments in both customary and conventional IHL applicable during NIAC have influenced its material scope and, in particular, the level of organization armed groups require in order to qualify as a Party to a NIAC. Following from the conclusions of sections four and five, the sixth section assesses the continued relevance of the distinction between CA3 and APII NIACs in practice.