One key area in which international humanitarian law (IHL) needs strengthening is the protection of persons deprived of their liberty in relation to non-international armed conflicts (NIACs). While the Geneva Conventions contain more than 175 rules regulating deprivation of liberty in relation to international armed conflicts in virtually all its aspects, no comparable legal regime applies in NIAC. Since 2011, States and the International Committee of the Red Cross (ICRC) have worked jointly on ways to strengthen IHL protecting persons deprived of their liberty. Between 2011 and 2015, the ICRC facilitated consultations to identify options and recommendations to strengthen detainee protection in times of armed conflict; since 2015, the objective of the process has shifted towards work on one or more concrete and implementable outcomes. The present note recalls the legal need to strengthen detainee protection in times of NIAC and the main steps that have been taken over the past years to strengthen IHL.