The book "The longest afternoon: the four hundred men who decided the Battle of Waterloo" tells the true story of how a small group of British and German soldiers defended a farmhouse called La Haye Sainte during the Battle of Waterloo. Despite being vastly outnumbered, these soldiers held off many thousands of French troops and played a crucial role in changing the course of history. The book captures the fear, chaos, and uncertainty of battle through eye-witness reports, highlighting the determination, cunning, and fighting spirit of these ordinary soldiers who made a significant impact on the outcome of the battle.