When there was a battle to be fought, these warriors were there: gladiators, conquistadors, ninjas, Vikings . . . From Roman arenas to the lawless high seas, this series for readers age 12 and up spotlights the world's most fearsome combatants. Each title surveys the history of a fighting group, examining key leaders, weapons, skills, rules of warfare, and reasons for existing. In the 14th and 15th centuries, while Japan's samurai fought high-profile battles in the open, stealthy ninjas fought in the shadows. Serving variously as mercenaries, spies, and guards, the highly trained, secretive warriors carried out guerilla operations under the cover of darkness at the service of warlords. This title for readers age 12 and up surveys the history of the ultra-quiet martial arts masters. It covers key fighters, weapons, combat skills, and rules of warfare. Includes a glossary, sidebars, index, and further resources.