The Art of War is an ancient Chinese military treatise dating from the Late Spring and Autumn Period. The work, which is attributed to the ancient Chinese military strategist Sun Tzu ("Master Sun", also spelled Sunni), is composed of 13 chapters. Each one is devoted to a different set of skills (or "art") related to warfare and how it applies to military strategy and tactics. The book contains a detailed explanation and analysis of the 5th-century BC Chinese military, from weapons and strategy to rank and discipline. Sun also stressed the importance of intelligence operatives and espionage to the war effort. Considered one of history's finest military tacticians and analysts, his teachings and strategies formed the basis of advanced military training for millennia to come.