It was a position too strong to be carried by assault, the British soon learned, but could not the entire embankment be blown into the air from below, if not from above? It would take time, courage, and skill. Underground tunnels would have to be dug from the British lines long distances to the ridge and under it, but the feat might be successfully performed. For nearly two years several corps of Australian, New Zealand, and British sappers tunneled and dug and finally located nineteen mines containing a million pounds of ammonite.

On June 7, 1917, after two weeks of artillery "preparation" of the position, the mines were exploded with complete success and over the fragments swept an infantry attack directed by Sir Henry Plumer, one of the most successful of the British field generals of the war. In a few minutes the German lines on a front of ten miles were captured. It is more correct to say that the site where they had been was captured, for there were no trenches or dugouts left. The British occupied the spot where the German lines had been. Then followed the storming of Messines Ridge itself, the second German line. The forests, which the Germans had calculated would shelter them, were burned down by streams of blazing oil. Within three hours the second line was carried, and by the end of the day the rear defense line fell, so that the entire salient was wiped out in one of the most gallant actions of the war.

An eyewitness thus described the assault. "All through the night the sky was filled with vivid flashes of bursting shells. From an observation post I watched this bombardment for that moment when it should rise into a mad fury of gun fire, before the troops, lying in those fields, should stumble forward. The full moon had risen, veiled by vapors. The drone of a night-flying aëroplane passed overhead. The sky lighted a little and showed great smudges like ink blots on blue silk cloth, where the British kite balloons rose in clusters to spy out the first news of the coming battle.

"The cocks of Flanders crowed. Out of the dark ridges of Messines, gushed up enormous volumes of scarlet flame from exploding mines, and of earth and smoke, all lighted by flame spilling over into fountains. Fountains of fierce color so that the countryside was illuminated with red light. . . . The ground trembled and surged violently . . . Thousands of British soldiers were rocked like that before they scrambled up and went forward to the German lines." As day broke, rockets rose from the latter, distress signals white, red, and green, flung up by the few who still lived in that zone of fire.

To the troops engaged, one of the most extraordinary thrills of this battle was the moving forward of the gun batteries from the positions they had held for two years and a half. When the good news came of the success of the attack, the signal was given, the horses were harnessed to the gun limbers and dashed out at a gallop, past the old screens, up the slopes they had watched so long. And from thousands of hot, dusty throats rose a great cheer, sweeping along the British front, as they watched the gunners go up the ridge, where they unlimbered in new positions and began a new phase of the fighting. As an eyewitness said: "There had been up to that time nothing like it in excitement and sense of victory."

The aviators performed astonishing feats. They attacked not merely German aëroplanes but the German troops. Flying far over the German lines, they swooped down upon groups of men on the march and killed them with machine gun fire from the air; one man thus destroyed a large body of troops preparing a counter-attack. He then cleared out a whole trench full of German soldiers, who scuttled like rabbits for their dugouts. Other aviators swooped down upon the German batteries, killing the crews with machine gun fire. One airman swooped so low he cleared a motor car by only four feet, splashing bullets all round the car as he passed, and barely saved his own machine, as the driver steered the car into a ditch, where it upset.