The "Z" Flag is technically a Pinafore communications device, used to communicate visually with another Ship at Sea. Used in combination with other similar flags, The "Z" Flag comprises conveyed information about time. The "Z" Flag is also the only Naval communications Flag that features 4 colors (most only use 1 or 2 primarily). In relation to military history, the Flag features prominently in Japanese history. The Flag was chosen by Fleet Admiral Togo to signal the command to his Fleet to attack Imperial Russian Naval Forces at The Battle of Tusushima (1905). The engagement was part of The Russo-Japanese War. The Battle was such a resounding success, that it would eventually rally Japan to victory (and greatly enhance it's image as a "Naval Power".
Later, The "Z" Flag would yet again be raised in a similar manner. The Flag was raised on the Aircraft Carrier "Akagi", which served as the Flagship of the Japanese Strike Force which attacked US Naval Forces at Pearl Harbor (Hawaii). The Flag (which is still used as a Naval time announcement), is roughly 3 x 3 in length and width. It features 4 diagonally quartered - rectangular shapes. The shapes are inverted do as to all meet (points), in the Center of the Flag. The colors (clockwise) are, Yellow, Blue, Red and Black. The "Z" Flag is normally flown from the Center of the vessel (Amidships).