The movements of a different kind were those designed at one point or another to drive a wedge or salient into the Allied front. In the operations on the German flank between the Aisne and the Belgian coast there have been two main efforts of that character. The first was the attempt to split the Allied front at Roye and at Arras, and to break up the line between those places; the second was the effort on an even larger scale, and pursued with still greater determination, to split the front at La Bassée and at Ypres, and to break up the line intervening. It is no mere accident that this latter attempt followed immediately on the failure to cross the Yser. _The attempt arose out of the necessity of the situation._ On the Upper Meuse, by another great effort, the Germans had driven a wedge into the French fortified frontier at St. Mihiel, and that wedge appeared to some the prelude of a mysterious scheme. In fact, the intention and the effect of it was to hold off the French advance along the frontier of Lorraine and across the Vosges. Again it is the case of a desperate man clinging to a railing. We have, therefore, three great efforts to break the Allied front by their wedge tactics, and three to outflank the Allied outflanking development. None of these efforts succeeded. What was the consequence? The consequence was that the German armies in France and Belgium could neither advance nor retreat. They could not advance because they are not strong enough. They could not retreat, because retreat would mean their destruction. The retreat of any army--and most of all the retreat of a huge mass army--is not a simple matter. On the contrary, it is a most difficult and complex operation in the most favourable circumstances. Here, however, was not one mass army, but a line of mass armies, occupying a front forming a right angle, and opposed on each arm of that right angle by forces which had proved stronger than they. So situated, they could only retreat with any chance of safety by falling directly back; but either arm of the angle if it fell directly back must obstruct the retreat of the other; and if they fell directly back each at the same time, their movements must become exactly like those of the blades of a pair of scissors as they are being closed. _A retreat under such conditions is a military impossibility._ Not a few fantastic motives have been attributed to the Germans, more particularly as regards the terrible struggle in West Flanders, but the plain truth of the matter is that here stated. Now if we turn to the strategy of the Allies, bearing their governing motive in mind, we shall find that it rested primarily on the attack launched against the German positions north of the Aisne and round Rheims.