Karate is not a martial art. Neither is judo, aikido and many other of the, uh, whatever-they-are arts. OK, fighting arts.
Strictly speaking, ‘martial’ is something that pertains to war. So martial arts are war arts.
In feudal Japan, martial arts would include systems using swords, spears, bows and arrows, even later guns and other weapons.
A samurai on the battlefield would not willingly give up his weapons. If he, through really bad luck, lost his long sword, short sword and knife, he might resort to last-ditch grappling. This is where some of the first ju jitsu moves came from.