peacekeeper          
noun [ C ] uk/ˈpiːsˌkiː.pər/ us/ˈpiːsˌkiː.pɚ/
 调停者;维和人员
a person who tries to prevent or stop arguments or fighting between two or more people or groups
  At school he was what they call a peacekeeper. He would always make sure everyone was getting along. 在学校里,他是大家所谓的和事佬,总是确保每个人都融洽相处。 
  维和部队士兵
a member of an international military force whose job is to prevent or stop fighting in a place
  UN peacekeepers were brought in to the troubled area. 联合国维和部队被派往动乱地区。 
 Since then, the territory has been run by the UN and protected by about 8,000 international peacekeepers.  从那时起,这片领土一直由联合国管理,并由约8000名国际维和士兵保护。 
 - More examples
 - The union leader has acted as a peacekeeper in the industry, working with industry executives to reduce labour costs.
 - He was a former Los Angeles gang member who became a peacekeeper respected by street toughs as well as by law enforcement agencies.
 - United Nations peacekeepers have served in volatile and often controversial missions.
 - The United Nations has deployed about 750 peacekeepers in the streets, according to news dispatches.
 
See: peacekeeping