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.
The details of the movement were therefore of little moment, and owed the attention they attracted to the habit of measuring progress in war by miles marked on a map. It was the end of January before the preliminary operation of clearing the Beaumont-Hamel spur was completed, and the apparently substantial advance began with the fall of Grandcourt on 7 February. A more ambitious attack on Miraumont from the south of the Ancre was somewhat disconcerted on the 17th by a German bombardment of our troops as they assembled, although the night was dark and misty; for even in France the Germans found spies to work for them, and a number of executions for treachery failed to prevent knowledge of our plans from occasionally reaching the enemy. A week later the German retreat extended, and Warlencourt, Pys, Miraumont, and Serre were evacuated. Again the Germans stopped for a time to breathe, and it was not till 10 March that Irles, a bare mile from Miraumont, was abandoned. By that time the Germans had only rearguards and patrols left either north or south of the Somme, and when on the 17th a general Allied advance was ordered it encountered little resistance. The area of the German withdrawal had spread over a front of a hundred miles from Arras in the north to Soissons in the south. On that day British troops occupied Bapaume, while the French, whose line we had taken over as far as the river Avre, proceeded to liberate scores of villages between it and the Aisne. On that day, too, by one of the apparent illogicalities of French politics, M. Briand's Cabinet, which had held office for the unusual period of eighteen months, resigned.
The German tide rolled sullenly and slowly back for another fortnight. Pronne, Nesle, and Chaulnes fell on the 18th, Chauny and Ham on the 19th, and on the 20th French cavalry were within five miles of St. Quentin. By the end of March the British line ran from a mile in front of Arras to the Havrincourt wood, some seven miles from Cambrai, and thence southwards to Savy, less than two miles from St. Quentin. Thence the French line ran to Moy on the Sambre canal, behind La Fre, which the Germans had flooded, and through the lower forest of St. Gobain to the plateau north-east of Soissons. The German resistance had gradually stiffened, and there was a good deal of local fighting in the first week of April while the Allies were testing the strength of the positions behind which the Germans had taken shelter. We called them the Hindenburg lines, and believed that the Germans had so named them to give them a nominal invincibility which they did not possess in fact. In Germany they were known as the Siegfried lines, a name which properly only applied to the sector between Cambrai and La Fre which was also protected by the St. Quentin canal. That was the front of the new German position; its flanks rested on the Vimy Ridge to the north, and on the St. Gobain forest and the Chemin des Dames to the south. It was a better and shorter line than that which the battles of 1914 had left to the combatants without much choice on either side, and the Germans were right enough in claiming that the Hindenburg lines were selected by themselves. Their retreat thereto was not, however, a matter of choice except in so far as they preferred it to the disaster which would otherwise have overtaken them in their more exposed positions. As a retreat the movement could hardly have been more successfully carried out; but the military distinction was marred by moral disgrace. For destruction was pushed to the venomous length of maiming for years the orchards of the peasantry in the abandoned territory. The crime may have been no more than a characteristic expression of militarist malevolence and stupidity; but it may also have been calculated to bar the path to peace by agreement and to force on the German people the choice, as a Junker expressed it later, between victory and hell.
The success of the German withdrawal discounted our spring offensive, not because any attack was designed on the Somme, but because the Hindenburg lines and the desert before them gave that part of the German front a security which enabled the German higher command to divert reserves from its defence to that of the threatened wings. Here preparations had been begun by both the French and the British before the German retreat, and it had barely reached its limit when on Easter Monday, 9 April, Haig attacked along the Vimy Ridge and in front of Arras. Since 21 March a steady bombardment had been destroying the German wire defences and harassing their back areas, and in the first days of April it rose to the pitch which portended an attack in force. Since the battle of Loos in September 1915 our front had sagged a little, and points like the Double Crassier had been recovered by the Germans. So, too, the French capture of the Vimy heights, which had been announced in May that year, proved something of a fairy tale, and in April 1917 our line ran barely east of Souchez, Neuville, and the Labyrinth. It was held by Allenby's Third Army, which joined Gough's Fifth just south of Arras, and by Horne's First, which extended Allenby's left from Lens northwards to La Bassee. The Germans had three lines of defences for their advanced positions, and then behind them the famous switch line which hinged upon the Siegfried line at Quant and ran northwards to Drocourt, whence quarries and slag-heaps linked it on to Lens (see Maps, pp. 79, 302). This line had not been finished at the beginning of April, and hopes were no doubt entertained that complete success in the battle of Arras, reinforced by Nivelle's contemplated offensive on the Chemin des Dames, would break these incomplete defences and thus turn the whole of the Hindenburg lines.
At dawn on Easter Monday the British guns broke out with a bombardment which marked another stage in the growing intensity of artillery fire, and obliterated the first and then the second German line of trenches along a front of some twelve miles. To the north the Canadians under Sir Julian Byng carried the crest of the Vimy Ridge, and by nine o'clock had mastered it all except at a couple of points. Farther south troops that were mainly Scottish captured Le Folie farm, Blangy, and Tilloy-lez-Mofflaines, while a fortress known as the Harp, and more formidable than any on the Somme, was seized by a number of Tanks. The greatest advance of the day was made due east of Arras, where the second and third German lines were taken and Feuchy, Athies, and Fampoux were captured. On the morrow the Canadians completed their hold on the Vimy Ridge, and Farbus was taken just below it. On the 11th the important position of Monchy, which outflanked the end of the Siegfried line, was carried after a fierce struggle; and on the 12th and the following days the salient we had created was widened north and south of Monchy. The capture of Wancourt and Heninel broke off another fragment of the Siegfried line, while to the north our advance spread up to the gates of Lens; the villages of Bailleul, Willerval, Vimy, Givenchy-en-Gohelle, Angres, and Lievin, with the Double Crassier and several of the suburbs of Lens, fell into our hands. The Germans appeared to have nothing left but the unfinished Drocourt-Quant switch line between them and a real disaster.
The battle of Arras was the most successful the British had fought on the Western front since the Germans had stabilized their defences. Our bombardment was heavier than the enemy's, and was far more effective against his wire entanglements and trenches than it had ever been before; and the new method of locating hostile batteries by tests of sound enabled our gunners to put many of them out of action. Nor throughout the war was there a finer achievement than the Canadian capture of the Vimy Ridge or the British five-mile advance in a few hours to Fampoux. The German losses in men and guns also exceeded any that the British had yet inflicted in a similar period; in the first three days of the battle some 12,000 prisoners and 150 guns were taken. The battle did not succeed in converting the war from one of positions into one of movement; but if the Vimy position could be so completely demolished in two or three days, there seemed little prospect of permanence for any German stronghold in France, and a few repetitions of the battle of Arras bade fair to make an end of the Hindenburg lines and of the German occupation of French territory. April along the Western front in 1917 wore a fair promise of spring.
Nor was it without its hopes in other spheres. Maude's conquest of Baghdad produced other fruits in the East, including a welcome change in the situation in Persia. The fall of Kut in the April before had enabled the Turks to turn against the Russians and drive Baratov's adventurous force back from Khanikin into the mountains and even east of Hamadan; but Maude's advance cut the Turks off from their base at Baghdad and threatened their line of retreat to Mosul. The Turks were in a trap: Baratov resumed his advance from the north-east, while Maude pushed up from the south-west: Khanikin was the trap-door, and Halil, the Turkish commander, made skilful efforts to keep it open. A strong screen of rearguards held up the Russians at the Piatak pass, while other troops reinforced from Mosul barred Maude's advance at Deli Abbas and on the Jebel Hamrin range. By the end of March the bulk of Halil's forces were through, and Maude had to content himself with linking up with the Russians at Kizil Robat and driving the Turks from the Diala after their troops in Persia had escaped. Their junction with those from Mosul enabled Halil to resume the offensive, but his counter-attack was repulsed on 11-12 April, and Maude proceeded to extend his defences far to the north and west of Baghdad. Feluja on the Euphrates had already been occupied in March, and the Turks driven up the river to Ramadie; and on 23 April Maude completed his advance up the Tigris by the capture of Samara, where the section of the railway running north from Baghdad came to an end. Hundreds of miles separated it from the other railhead at Nisibin, and with his front pushed out on the rivers to eighty miles from Baghdad, and with the Russians in touch with his right and holding the route into Persia, Maude might well rest for the summer content with the security of his conquests. He had done single-handed what had been planned for a joint Anglo-Russian campaign, with Russia taking the lion's share (see Map, p. 177*).
In the spring of that year it looked, indeed, as though the British Empire alone was making any headway against the enemy Powers. Even on the cosmopolitan Salonika front offensive action was left to British troops, and at no time during the war did any but troops of the British Empire partake in the defence of its dominions and protectorates. These were all safe enough by the middle of April 1917, and those that were within reach of the enemy were being used as bases for attack upon his forces. Maude, with his army based upon India had now blocked the southern route into Persia, and Sir Archibald Murray was advancing into Palestine. The capture of Rafa on the frontier was followed on 28 February by that of Khan Yunus, five miles within the Turkish border, and the Turks under their German general Kressenstein withdrew to Gaza. There, on 26 March, they were attacked by Sir Charles Dobell, of Cameroon fame, with three infantry and two mounted divisions, including a number of Anzacs. The design was to surround and capture the Turkish forces in Gaza, and the only chance of success lay in the suddenness of the blow and its surprise. For Dobell's base was distant, his men had to drink water brought from Egypt, and in spite of the railway he had not at the front stores, equipment, or troops for a lengthy struggle, while the Turks could bring up superior reinforcements. A sea fog robbed him of two hours' precious time; and although the Wady Ghuzze and other defences of Gaza were taken and a force of Anzacs actually got behind Gaza and were fighting in its northern outskirts at sunset, night fell with the task unfinished and the British divisions out of touch on their various fronts. A retirement was accordingly ordered, and on the morrow Kressenstein counter-attacked. He was driven back with considerable losses, and although Dobell had failed to take Gaza he had reached the Wady Ghuzze and secured the means of bringing his railhead right up to the front of battle. With a few weeks' respite for reinforcement and reorganization, April might yet see the British well on the way to Jerusalem; for Arras was not intended to stand alone, and in every sphere of war the Allies had planned a simultaneous offensive (*see Map, p. 352*).
But if hope was bright in the East, it was pallid compared with the certainty of ultimate triumph which blazed from the West across the Atlantic; for on the 5th of that April of promise the great Republic, with a man-power, wealth, and potential force far exceeding those of any other of Germany's foes, entered the war against her and made her defeat unavoidable save by the suicide of her European antagonists. It was not a sudden decision, for a people with such varied spiritual homes as the American, spread over so vast a territory, and looking some eastward across the Atlantic and others westward across the Pacific, but all far removed from European politics and cherishing an inherited aloofness from the Old World and a rooted antipathy to imperialisms of every sort, could not easily see with one eye or achieve unanimity in favour of a vast adventure to break with their past and unite their fortunes with those of the Old World they had left behind. We were accustomed to fighting in Europe against overweening power; the United States had taken their stand on a splendid isolation. Their first president had warned them against entangling alliances, and their fifth had erected into the Monroe Doctrine the principle of abstention from European quarrels. For a century that principle had been the pole-star of American foreign policy; no other people had such a wrench to make from their moorings before they could enter the war, and no other people can understand what it cost the Americans to cut themselves adrift from their haven of democratic pacifism in order to fight for the freedom of another world.