The French Nieuport company provided the Allied air forces with the first true fighter scout of World War 1 in the shape of the diminutive XI of 1915.Based on the Bebe racer, built for the abandoned Gordon-Bennett Trophy of the previous year, the aircraft utilised a sesquiplane (lower wing much smaller than the upper wing) arrangement which gave the XI extreme manoeuvrability. It was the only scout respected by the all-conquering German Fokker E-series of 1915-16, and was flown by French, British, Russian, Belgian and Italian aces. This book explores the exploits of these aces in combat.The XI was replaced from May 1916 onwards by the bigger and more powerful XVII. which proved to be one of the best fighters of World War 1.