In November 1916 a conference of representatives of all the Allied Powers was held at French General Headquarters, and a plan made for the campaign of the following year. In 1917 Sir Douglas Haig desired to undertake a great offensive in Flanders, with a view to clearing the Belgian coast, for in that area he believed that success would give the highest strategic reward. But before this movement began it was desirable to reap the fruits of the Battle of the Somme. In November the enemy was penned in an awkward salient between the valleys of the Ancre and the Scarpe. The British Commander-in-Chief proposed early in the spring to attack this salient simultaneously on two sides—the Fifth Army moving on the Ancre front, and the Third Army attacking from the north-west about Arras. At the same time the First Army was to carry the Vimy Ridge, the possession of which was necessary to secure the left flank of our operations farther south. So soon as this was completed, the Flanders campaign would begin with an assault on the Messines Ridge, to be followed by an attack eastward from the Ypres salient. The reasons for Sir Douglas Haig’s plan are clear. He was fully aware of the new great German position which had been preparing during the winter, and which was known as the Hindenburg or Siegfried Line, and he did not think it good policy to make a frontal assault upon it. He knew that the Battle of the Somme had seriously weakened the enemy, and he believed—it was, indeed, a mathematical certainty—that the tactics of the Somme, if persisted in during 1917, and supported by a reasonable pressure from the Russian front, would give the Allies victory before the close of that year. He wished, therefore, to stage a second battle of the Somme type—to stage it in an area where its strategic results would be most fruitful; and to begin it sufficiently early in the season to allow a decision to be reached before the close of the good weather.