Takeda Shingen

Takeda Shingen was one of the Big Three of the late Sengoku Era, including his legendary rival Uesugi Kenshin and Hojo Ujiyasu. Said to be a strategist of unparalleled genius and possible rival to the great Zhuge Liang as one of history's greatest strategists, Shingen is notable in that he was the first of the two great northern warlords, Kenshin being the other, who made their bid against Oda Nobunaga, only to die under mysterious circumstances before he could properly crush Nobunaga. His nickname is "Tiger of Kai". His clan is well known for their cavalry units, known as the strongest at that point, until that one certain day (read below further).

He's noted for being painted with a Gunbai (War fan) nearby. This is mostly taken from a story during the 4th battle with Uesugi Kenshin that Kenshin snuck into his camp, sword ready to kill Shingen, but then Shingen deflected all his attacks with a nearby fan.

He made his bid to the capital earlier than the rest, and the first to get in his way was none other than Tokugawa Ieyasu, currently an ally of Nobunaga. Shingen trounced Ieyasu pretty badly in Mikatagahara, forcing him to retreat, but Shingen failed to kill him. While continuing the march, however, Shingen fell into a mysterious sickness and eventually died en route, to be succeeded by his son Katsuyori, who while a good war general, isn't as capable as a daimyo, resulting into a disastrous battle in Nagashino, whereas Nobunaga utilizes his musket strategies to utterly annihilate the otherwise invincible Takeda Cavalry. Needless to say, the Takeda fell to ruins after that day, and Katsuyori committed seppuku in shame eventually. Shingen's death propelled his rival Kenshin to make his bid to the capital and eventually crush Nobunaga once until he also dies mysteriously.

Aside of his cavalry, war genius, gunbai and rivalry to Kenshin, Shingen is also known to invent the phrase/motto "Fuu-Rin-Ka-Zan". In combination of Sun Tzu's Art of War, it basically tells his army to "Move as swift as a wind, stay as silent as forest, attack as fierce as fire, undefeatable defense like a mountain." There's also some nasty rumors that Shingen also kept boiling pots around his camp, probably to punish prisoners of war with death. Considering the turbulent situation of the age, it is quite standard to have such degree of ruthlessness.