In medieval times, when Arabian conquerors subdued Northern Africa, the Tuareg were never conquered. The nomads left for the desert and vanished in the impassible sands of the Sahara from where they made plundering raids on Arabian settlements.
The Tuareg were the only people in the world whose men had to cover their face with a veil even in the family circle (the name itself "Kel Tamasheq" means "people of the cover").
The settled farmers from the few oases in the Sahara held many black slaves. These were numerous because the Tuareg controlled caravan routes through the desert, which slave-traders used to deliver the captured Africans to the Mediterranean coast.
The slaves tilled the land, tended herds and dug deep wells. Due to slave labor, the upper class Tuareg were able to spend enough time on combat training and attaining expertise that they became expert swordsmen.
They were few in number, but in battle due to their skill and physical training, they were superb.