At this time Great Britain had about 2,250,000 men under arms in France and Belgium. They were organized in five field armies, which in the spring of 1917 lay as fol lows, from north to south: In Belgium, the Ypres sector, the 2d Army under General Phimer ; in the Lys-Lens sector, the 1st Army under General Horne; in the Arms sec tor, the 3d Army under General Allenby, soon to be succeeded by General Byng; in the Bapaume sector, the 5th Army under General Gough ; and in the Saint Quentin sector, the 4th Army under General Rawlinson.• They were well-trained men, seasoned by the Somme and Arras fighting, the equal of the Germans and French in fighting qualities; and they were amply supplied with artillery and anununition.
The Germans on the same front were com manded at this time by the crown prince of Ba vana, who had risen steadily as a conunander since the war beg-an, somewhat to the discom fiture of the imperial crown prince, whose fail ure at Verdun was notable. From the North Sea to the region just south of Ypres lay the Gennan 4th Army, corrunanded by General von Arnim, who had come to be considered one of the best German commanders in the field. South of his command was the 6th Army under Gen. Otto von Below. The Germans had ample forces; for by this time the Russian front had become qtuet, and it was possible to move troops freely from that area to France. General von Anum was keen enough to ob serve signs of activity behind his opponents' lines late in May 1917 and rightly concluded that he was going to ge assailed in the Ypres region. He also divined that the attack would begin at the Wytschaete-Messines Ridge; for he could see that it was a thorn in the side of the British, who could not attack on a large scale without .first removing this obstacle.
General Plumer, commanding the 2d Army, was a vigilant and tireless officer, and he had been in position before the ridge for two years when the great attack was made. As early as July 1915 he began to construct mines under this position, taking advantage of the clay subsoil which lent itself to alining. Twenty-four mines were constructed, 20 of them in the zone it was at last decided to at tack. One of these was destroyed by the Ger mans, but the 19 others were intact and filled with over 1,000,000 pounds of ammonal when the critical day arrived. The Germans knew well that the mines were being constructed and countermined, and many battles were fought underground between the hostile mining parties.
Behind the lines railroads were constructed on the surface and pipes were laid for the distri bution of water m the trenches with provisions for carrying them forward as soon as the lines had been advanced. So well were the plans made that running sterilized water was deliv ered to the soldiers in half an hour after they had won a new objective.
The day of attack was 7 June, after a hurri cane of shell had been poured on the ridge for several days. The gins on the British side fell away somewhat durmg the night of the 6th, but the German guns continued to roar as on the preceding days. At 3:10 in the morning there was a convulsive shock and °a sotmd compared to which all other noises were silence)) Nineteen mines went off at once, flames rushing up like volcanoes, carrying trenches, concrete emplacements, solid stones and twisted human bodies in one fire-lit mass. Great clouds of heavy gases mushroomed the slcy and slowly drifted away as the artillery resumed its work.
Three army corps were in front of the ridge and sprang from their trenches at the first tremor of the explosion. They plunged forward into the clouds of smoke and dust, overran the first German line of defense, which had suf fered severely from the bombardment, and gained the crest of the ridge with 19 craters where the second line had been, from Hill 60 on the north to the edge of Messines on the south, a distance of more than four miles. Brave Germans held out in isolated positions, fighting despemtely in a dazed condition, but they slowly yielded to the advance of the men of the 2d Army. By 3 o'clock in the after noon the British field guns had been carried forward by a miracle of the transportation de partment, and the attack on the third line was made with such quick effect that by nightfall this position, the objective set by General Plumer for the first day of the battle, was fully reached. At an unexpectedly small cost to his own arrny he took 7,200 prisoners and 67 guns and inflicted a great loss on the enemy.
On the afternoon of the 8th General von Arnim brought up fresh troops and counterattacked along the new front, but they were beaten off easily by the British who consolidated their lines and settled down in the new trenches in security, two and a half miles in front of the position they had occupied for nearly three years.