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 Quéant 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.