This book is based on the author's experience of working for more than two decades in over thirty conflict and post-conflict zones. It is written for those involved in UN peacekeeping and the protection of civilians. It is intended to be accessible to non-lawyers working in the field who may need to know the applicable legal standards relating to issues such as the use of force and arrest and detention powers on the one hand and the delivery of life-saving assistance according to humanitarian principles on the other. It will also be of interest to scholars and students of peacekeeping, international law and international relations on the practical dilemmas facing those trying to operationalise the various conceptions of 'protection' during humanitarian crises in recent years.