a war fan is a fan designed for use in warfare. several types of war fans were used by the samurai class of feudal Japan. kunoichi (female ninja) used them also. they are also referred to as tessen (鉄扇).
In feudal times, the samurai's wife, or okugatasama (literally: the one who stays at home), looked after the children and chores, and defend the house from thieves and invaders while her husband was away in State or clan battles.