At the end of the nineteenth century, the great powers of the world waged wars of expansion. In the 37th year of the Meiji Period, Japan declared war against Russia and the Russo-Japanese War broke out. In this war, the telegraph was used for the first time in real battles. It is said that the wireless message of "Enemy ships in sight" from the Shinanomaru, which discovered the gigantic Baltic Fleet, led the Battle of the Japan Sea to victory.