The campaign had, however, tried the health and endurance of our forces, and three months' respite was now taken for recuperation and reinforcement before the final task of eradicating the Germans from the remnants of their territory. The great difficulty was that, apart from the Mahenge plateau, they were not rooted to any spot, and their elusiveness was illustrated by the fact that the Tabora garrison evaded the encircling forces and joined Von Lettow-Vorbeck at Mahenge. The campaign reopened on 1 January 1917, and consisted of a converging attack on Mahenge by Hoskins from Kilwa on the coast, by Northey from Lupembe, by Van Deventer from Iringa, and by Beves and subsidiary forces from north of the Rufigi. Smuts was summoned on the 29th to England to take part in the imperial conference, and Hoskins succeeded to the chief command. Unprecedented rains impeded our operations; progress became slow, and remained so after Van Deventer replaced Hoskins at the end of May. Not till October was Mahenge occupied by the Belgians. On 26 November half of the German forces under Von Lettow-Vorbeck's lieutenant Tafel were forced to surrender between Mahenge and the Rovuma; but Von Lettow himself escaped across the frontier with sufficient troops to terrorize the Portuguese and maintain himself in their territory until the end of the war. The victor in the East African campaign came in 1917 to a Europe where victory seemed also on the way, for the early spring saw the only German retreat of moment until the war was near its end. The battles of the previous September had convinced the Germans that their line upon the Somme was barely tenable, and they had employed the winter pause to perfect the shorter and better line upon which they had begun to work at Michaelmas. Possibly it was to frustrate these preparations that Haig reopened his campaign so early as he did. On 11 January, the day on which the Allies answered President Wilson's note, British troops began to nibble at the point of the salient on the Ancre which had been created by the battle of the Somme. It was a modest sort of offensive; for it was no part of the Allies' combined plan of operations, which had been settled in conference during November, to launch a first-class attack across the devastated battlefield of the Somme. That wasted area was as effective a barrier as a chain of Alps to military pressure, and the Germans were thus left free to withdraw from their salient without much risk of disaster. They did not contemplate any serious stand, and until the Allies were ready to strike at the flanks of their position the Germans could afford to retreat at a pace which was not seriously hustled by our advance. They showed as much promptitude, foresight, and skill in retirement as they had done in their advance; they suffered few casualties and had no appreciable loss in guns or prisoners.