The distinctive blue helmets and berets of UN peacekeepers have featured prominently in many conflicts since their missions began in 1956. Originally tasked with monitoring cease-fires, the role of UN troops has since evolved to include to peace enforcement (often with mixed results). On March 28, the UN passed a resolution to allow a peacekeeping brigade in the Democratic Republic of Congo to engage in offensive combat against rebel factions, making it the first UN peacekeeping mission authorized to use such force. (15 PHOTOS)