On June 7the 1917, General Sir Herbert Plumer's Second Army smashed the impregnable German defences along the Messines-Wytschaete Ridge in an assault where technology and innovative thinking were combined to produce an extraordinary success. Until 1918, Messines was the only clear-cut Allied victory on the Western Front. The victory came at a time when Britain and her allies needed it most; it boosted Allied morale and shattered that of the Germans. It was also a battle which brought together a commonwealth of nations, including Irishmen and Ulstermen, fighting alongside each other to defeat a common enemy. Plumer planned the battle as a composer might write the score of a symphony and assembled an orchestra of war, with each instrument - artillery, engineers, infantry, tanks, aircraft and administrative units - playing its part at the right time to overwhelm the enemy. Messines became the first true all-arms modern battle. This detailed account of the battle for the Messines-Wytschaete Ridge examines it from the British/ANZAC and German perspectives. It explores why the name of Messines is not as familiar as The Somme, Passchendaele or Verdun, and why General Sir Herbert Plumer is not as widely known as Field Marshal Sir Douglas Haig or even General Sir Hubert Gough. The author reassesses the reasons for General Plumer's success on the day, the implications of Haig's failure to exploit the success, and finally the legacy of the battle for the maturing of the BEF in 1918.