z flag
One of the international maritime signal flags. It is a square divided diagonally into four triangles, colored yellow, blue, red, and black. Also referred in NATO alphabet as "Zulu flag" (not the actual flag of the Zulu kingdom).
It represents the letter Z when communicating by individual letters. Combined with four number flags, it represents the time in UTC. On its own, it may mean "I require a tug" or "I am shooting nets".
The Z flag is of special significance in the context of Japanese naval history due to its role in the Battle of Tsushima where it was raised on the flagship Mikasa. In this battle, the Z flag was understood to mean, "The fate of the Empire rests on the outcome of this battle. Let each man do his utmost". However, the flag has gradually gained more notoriety after it was used as a signal flag of the Attack on Pearl Harbor on board the flagship Akagi, along with being a battle flag in several major engagements in World War II (including the last voyage of the battleship Yamato during Operation Ten-Gou). As a result, much like the Imperial German war flag, it has turned into a symbol for far-right Japanese ultranationalism.