The British had meanwhile been pressing forward on the Somme, and by July 23, 1916, had penetrated the German third line. The Russians too were winning successes, and had dealt a destructive blow in Volhynia. The pressure from the east and west forced the Germans to withdraw large bodies of troops from the Verdun sector and send them to the relief of their brothers on other fronts. In the closing days of July, 1916, the Franco-British "push" became the principal German preoccupation. The great struggle for Verdun, the longest battle continuously fought in history, from that time on became a military operation of only second importance. The magnitude of this great struggle may be illustrated by a few statistics. In the six months' combat some 3,000 cannon had been brought into action. About two millions of men had attacked or defended the stronghold. No correct estimate can be made of the losses on both sides, but it is stated that at least 200,000 were killed, and the end was not yet in sight. The second anniversary of the war found the Germans on the defensive. Twenty million fighters had been called to the colors of twelve belligerent nations; about four million had been killed, and over ten million wounded and taken prisoners. For all this vast expenditure in blood and treasure no decisive battle had been fought since the German defeat on the Marne in September, 1914. CHAPTER XLVII SPRING OPERATIONS IN OTHER SECTORS While greater issues were being fought out in the Verdun sector, from the beginning of the second phase of the German attack during March, there was considerable sporadic "liveliness" on other parts of the western front. Though the main interest centered for the time around the apparently impregnable fortresses of which Verdun is the nucleus, a continuous, fluctuating activity was kept in progress along the whole line up to the opening of the big allied offensive on the last day of June. March 1, 1916, found the battle line practically unchanged. From Ostend on the North Sea it ran straightway south through the extreme western comer of Belgium, crossing the French frontier at a point northwest of Lille. From there it zigzagged its way to a point about sixty miles north of Paris, whence it then followed an eastern tangent paralleling the northern bank of the River Aisne; thence easterly to Verdun, forming there a queer half-moon salient arc with the points bent sharply toward the center. From the south of Verdun the line extended unbroken and rather straight south and a little easterly to the Swiss frontier.