Peacekeeper
WordNet
noun
(1) The pistol of a law officer in the old West
(2) Someone who keeps peace
"She's the peacekeeper in that family"
(3) A member of a military force that is assigned (often with international sanction) to preserve peace in a trouble area
WiktionaryText
Noun
- someone who preserves the peace
- a member of a military force charged with peacekeeping duties in a troublespot