Greenmantle

"Greenmantle" by John Buchan is an early 20th-century novel that unfolds amidst the chaos of World War I, following Major Richard Hannay and his band of brothers on a high-stakes mission. When Hannay, recovering in the countryside, is summoned by Sir Walter Bullivant, he's thrust into a shadowy operation to prevent a potential holy war that could greatly harm the British Empire. Enlisting the help of the quick-witted Sandy Arbuthnot and the astute John S. Blenkiron he races against time through a world of complex international tensions and war's uncertainties.