It was not a struggle in which there was much scope for strategy on either side, because there had been no fixed data on which to base it. Each combatant had been bent on out-flanking the other before the sea was reached and success denied; but neither knew from day to day or hour to hour where his own or the enemy's line would be. It was idle to plan at headquarters the investment of places which might at the moment be well behind the lines, or the defence of others which the enemy might already have passed; and the alleged inexplicable nature of the German strategy seems to be largely due to an antedating of the establishment of a line of battle. They might have done better to concentrate on Arras with a view to breaking the Anglo-French liaison on the La Bassée Canal and isolating the British Army, than to distribute their onslaughts over a front of a hundred miles. But the problem was to outflank a wing which was still in the air, and not to break a line which was not yet formed; and even if it were in existence, subsequent experience would have justified the conviction that success was to be obtained by pressure along an extended front rather than by concentration on limited sectors like Verdun, or even the 18-mile front of the battle of the Somme. The struggle which closed the autumn campaign in the West was not, in fact, a new battle fought on a preconceived plan, but the final clash of armies seeking to outmarch each other's flanks in a battle begun on the Marne; and the popular German advertisement of a new campaign against the Channel ports and a different enemy than the French was merely a fresh coat of paint designed to cover a structure that had gone to pieces.