A fleet review is a traditional gathering of ships from a particular navy to be observed by the reigning monarch or his or her representative, a practice allegedly dating back to the 15th century. Such an event is not held at regular intervals and originally only occurred when the fleet was mobilised for war or for a show of strength to discourage potential enemies. However, since the 19th century, they have often been held for the coronation or for special royal jubilees and increasingly included delegates from other national navies.