The Protection of Civilians (PoC) has been part of United Nations (UN) peace operations for twenty years. Today, PoC is irrefutably a ‘centre of gravity’ for how UN peace operations see and portray themselves. Despite negative perceptions, a great deal of progress has been made in how missions prepare for and respond to the demands of protection mandates. For the vulnerable populations they serve, mandates to protect raise expectations and provide hope that peacekeepers will safeguard them. Yet efforts to implement PoC mandates have encountered a range of problems, which peace operations have struggled to address. This article critically reflects on the past two decades of promoting, planning for and practicing protection in UN peace operations. It argues that while the achievements are many, significant challenges remain and much more must be done to deliver on this cardinal obligation.