Dejma
The Dejma (Maltese: Id-Dejma) was a 14th century mercenary combatant force dedicated to protect the Maltese Islands in case of an Ottoman raid on one or more of the island's towns. The first reference to this was in 1462. Duties 
In the case of an attack on the islands, a fire would be lit on top of the several watchtowers on the Maltese Coast. The smoke from the fire (or the fire itself if it was night) would be seen from other watchtowers, who would do the same. This cycle would be repeated until all of the watchtowers were alerted. Upon seeing the smoke (or fire), the soldiers themselves would meet up at various designated locations around the islands. These locations would be marked by a customary "Dejma Cross" (Maltese Salib Tad-Dejma). Upon arriving, the soldiers would prepare for battle. The civilians, on the other hand would make their way to one of the two fortified cities: Mdina or Cittadella. (Valletta too if the attack occurred after the Great siege.) References 

Knights Hospitaller
Knights of Malta
History of Malta