sentences:  The reverse has a design featuring the Union Flag, surrounded by a circlet bearing the inscription FOR OPERATIONAL SERVICE, on top of a four pointed star representing the four cardinal points of the compass; in between the points, in line with the saltire of the Union Flag, are four coronets, representing the Crown and the three armed services - Royal (top left), Naval (Royal Navy, top right), Mural (British Army, bottom left), and Astral (Royal Air Force, bottom right).The ribbon for each version of the medal follows the same format, with a wide red bar in the centre, flanked on each side by navy blue, and then light blue bars, representing the three services, with on the edge bars of a unique colour - green (Sierra Leone), buff (Afghanistan), ochre (Democratic Republic of Congo), grey (Iraq and Syria).The first OSM to be awarded was for service during Operation Palliser, the United Kingdom's intervention in the Sierra Leone Civil War from May 2000 to July 2002.