That, it will be remembered, was a fateful day. At five o'clock on the afternoon before (everybody was perfectly specific about the hour), there had begun the great movement now known as the Second Battle of Ypres (or of the Yser). The assault had begun with the terrifying surprise of poison-gas; the gas was followed by artillery attacks of a ferocity hitherto unequalled; Ypres had been wiped out in a few hours; the Germans had crossed the Yser. Thus the French and English lines, which were joined, had been abruptly pushed back over a long front. That these were anxious hours for the Allies, Sir John French's report of June 15 (1915) indicates very plainly, I think. But they were far from being idle hours. To-day the whole back country, which for weeks had swarmed with soldiers, was up. For miles around, Allied reserves had been called up from camp or billet; and now they were rushing forward to stiffen the wavering lines and stem the threatening thrust for the coast. At three o'clock on this afternoon, I stood in Rue d'Ypres, before the railway station in Poperinghe, and watched the new army of England go up. Thousands and thousands, foot and horse, supply and artillery, gun, caisson, wagon and lorry, the English were going up. All afternoon long, in an unending stream, they tramped and rolled up the Flemish highroad, and, wheeling just before me, dipped and disappeared down a side-street toward "out there." Beautifully equipped and physically attractive--the useless cavalry especially!--sun-tanned and confident, all ready, I am sure, to die without a whimper, they were a most likely and impressive-looking lot. And I suppose that they could have had little more idea of what they were going into than you and I have of the geography of the nether regions. This was on my left--the English going up. And on my right, the two streams actually touching and mingling, the English were coming back. They did not come as they went, however. They came on their backs, very still and remote; and all that you were likely to see of them now was their muddy boots at the ambulance flap. Service Sanitaire as we were, I think Section 1 never saw, before or since, such a conglomeration of wounded as we saw that day at Poperinghe. Here was the rail-head and the base; here for the moment were the Red Cross and Royal Army Medical Corps units shelled out of Ypres; here was the nervous centre of all that swarming and sweating back-of-the-front. And here, hour after hour, into and through the night, the slow-moving wagons, English, French, and American, rolling on one another's heels, brought back the bloody harvest. [Illustration: SOLDIERS MARCHING BY AMERICAN AMBULANCES IN A FLEMISH TOWN]