Cambrai Offensive
On 1 August, the day when the offensive was supposed to begin, Haig was questioned by his generals as to the readiness of his tanks. At Ypres, the Germans were worried about another offensive, but they became even worried about an offensive at Cambrai when the artillery bombardment began on 25 July and hit several pillboxes. The British forces involved the 3rd Army and most of the troops from the 4th and 5th Armies. Troops facing the French, in Belgium, on their way to the east and reserves were transferred to Cambrai and the German 6th and 2nd Armies were readied to man the guns and defences of the Hindenburg Line. The offensive had to be postponed to permit the arrival of tanks to the frontline, but Haig wasted no time in getting the preparations ready. When the offensive kicked off the next day, the element of surprise was lost.
The battle initiated at about 06:00 on 2 August when the anticipated 1500 gun bombardment on German defences started, leaving smoke and a creeping barrage at 270 metres (300 yd) ahead to hide and support the first advance. However, efforts to conceal the attack were futile as the Germans received adequate intelligence to be on heavy alert when the major offensive was revealed to be against Havrincourt, with the usage of supporting tanks being anticipated. Lieutenant General Pulteney commanded the attacking force with six infantry divisions from the British III Corps on the right and on the left, the IV Corps, under General Woolcombe's command, assisted the nine battalions of the Tank Corps with about 400 tanks used. One infantry division in IV Corps and the three divisions of the Cavalry Corps, under Lieutenant-General Kavanagh, were placed in reserve for the anticipated breakthrough. Considerable success was experienced in the assault sectors initially and it was thought that a breakthrough would come; with the Hindenburg Line being pierced by fast tank and mobile advances. British 12th Division advanced as far as Lateau Wood before being ordered to consolidate. The British 20th Division reached La Vacquerie and then proceeded to take a bridge across the St. Quentin Canal. The bridge collapsed under the weight of a tank halting the hopes for an advance across the canal. In the centre, the British 6th Division captured Ribécourt and Marcoing before being repulsed by a German counter attack which chased the division back to its original positions.
On the IV Corps front, British 51st Division aimed to make its first objective Flesquières. This risked enfilade fire landing on the attacking divisions. George Montagnue Harper, the division's commander himself, had replaced his own tank drill for the standard one prepared by the Tank Corps; that and excessive distance between the tanks and the infantry resulted in his advance failing. It was apparent that Flesquières was among the toughest points of the Hindenburg line and was surrounded by other defence points. Its defenders under Major Krebs were capable of shelling enemy tanks, with approximately 50 being destroyed by artillery there. Some accounts even brought the dubious claim that five were destroyed by an artillery officer named Theodor Krüger's guns. The 'expert' came from a regiment and received praises even from Marshal Haig's dispatch in his diary despite the virtual lack of evidence although several sources might credit him with ten destroyed tanks. Thirty-eight tanks were lost in action on the first day after breaking down or being shelled by German artillery-fire. Haig believed that infantry was needed to bring the artillery crews under small-arms fire and permit freedom of tank operations. The typically recorded explanation of the "incredibly skilled" German officer ignored the fact that British tanks were resisted by the German 54th Division as they advanced because the German division received specialised training in anti-tank tactics and experience from fighting French tanks in the Nivelle Offensive. The Germans held Flesquières after repulsing every British assault at night.
To the west of Flesquières, British 62nd Division swept all the way through Havrincourt and Graincourt to within reach of the woods on Bourlon Ridge and on the British left, British 36th Division was halted before capturing the Bapaume-Cambrai road. Of the tanks, 200 were unable to attack after the offensive's first day, although only 80 were total losses or destroyed. Of the other casualties, 71 had suffered mechanical failure and 43 were abandoned. The German command quickly reinforced his sector, relieved that the British were incapable of exploiting or even maintaining their initial gains. When the battle restarted on 3 August evening, the pace of British advance was slackened greatly. Flesquièresand Cantaing were captured in the very early morning after being abandoned but in general the British took to consolidating their gains rather than expanding. IV Corps became the offensive's main effort as the III Corps was bogged down.
Bourlon Ridge was the aim of the offensive and fighting in that sector was heavy and costly around Bourlon and at Anneux (just before the woods). German counter-attacks from Moeuvres chased the British out on 3 August from the town and Fontain. After the capture of Anneux, the 62nd Division was shelled and blocked from entering Bourlon Woods. The British had placed themselves in a salient that was vulnerable to German counterattacks. Haig still demanded Bourlon Ridge's capture and the exhausted 62nd Division was reinforced by the 40th Division the next day. Assisted by 100 tanks and 450 guns, the 40th Division assaulted the woods of Bourlon Ridge on the morning of 5 August and made no progress after a German Corps arrived at the ridge with another three in reserve. The 40th Division attack reached the crest of the ridge before repulsion after receiving more than 5,000 casualties in four days. More British troops were sent as reinforcements to capture the woods, but the British reserves were decreasing quickly in the face of muddy ground, weather and German reinforcements. The final British attempt by the 62nd Division with 50 tanks began on 8 August, but the success was halted by German resistance, mud and rain. The British possessed a roughly 11 by 9.5 km (6.8 by 5.9 mi) wide salient and without reaping the benefits of their captures. The next day, the British troops were ordered to lay wire and consolidate as the offensive was halted. German artillery immediately focused on shelling the new British positions and fired more than 15,000 shells into the captured area next day.