After two years of disaster, a battle that changed everything. In the early hours of 7 June 1917, the quiet beneath Messines Ridge gave way to cataclysm. For months, British and Commonwealth tunnellers had waged a secret war underground, driving deep galleries beneath the German front line. Their objective was to break one of the strongest positions on the Western Front and restore momentum to an army stalled by years of costly failure. When nineteen vast mines detonated at dawn, the ridge erupted in fire and earth. Entire defensive systems were obliterated in seconds. Yet the greatest man-made explosion in history was only the opening blow. What followed was a brutal struggle across shattered ground and smoking craters as infantry fought to seize and hold the heights against fierce resistance and relentless counter-attack. For the Anzacs, who comprised one third of the attacking force, Messines proved the ultimate test. After crushing defeat at Gallipoli, Fromelles and Bullecourt, and horrendous casualties at Pozieres and Mouquet Farm, this was their first clear and decisive victory on the Western Front. For the men of the New Zealand Division, it would be their finest hour. For Australia’s newly formed 3rd Division under Major General John Monash, it was a harsh baptism of fire that would shape the remainder of the war. Drawing on extensive primary sources and international archives, Craig Deayton reconstructs the secret war beneath Messines and the savage fighting above it. He reveals how meticulous planning, engineering audacity and hard-fought infantry action combined to deliver the greatest British victory in three long years of war. Messines did more than take a ridge. It transformed the Anzacs. Praise “Meets all the criteria of good military history… clear analysis backed by an international review of primary sources.” — AIM Book Review “A comprehensive and thought-provoking account.” ‘Deayton brings the hidden war beneath the ridge into sharp focus. A significant and absorbing study.’