The green line objectives on the Plateau were not captured until the Battle of the Menin Road Ridge on 20 September, after the principal role in the offensive was transferred to the Second Army and three weeks' sunshine and fresh breezes dried much of the ground.

The Third Battle of Ypres became controversial while it was being fought, with disputes about the predictability of the August deluges and for its mixed results, which in much of the writing in English is blamed on apparent misunderstandings between Gough and Haig and on faulty planning, rather than on the resilience of the 4th Army.

[2] While the French recuperated, offensive action on the Western Front could only come from the BEF and in June 1917, the principle of a Flanders campaign was reluctantly approved by the British War Cabinet.

[3] On the French sector, Petain intended to maintain an active defence and planned three limited Batailles de Redressement (battles of recovery) lavishly to be supported with artillery, aircraft and manpower, sufficient to guarantee success and restore morale.

Passchendaele Ridge was to be taken and the advance continued to Roulers (Roeselare) and Thourout, to cut the Bruges (Brugge) to Kortrijk railway that supplied the 4th Army from Ypres to the Belgian coast.

[13] A preparatory bombardment was planned from 16 to 25 July and the Second Army was to capture outposts in the Warneton line, to simulate an advance beyond Messines Ridge and stretch the German defence.

[21] A planned slow build-up of Allied air activity over the Ypres Salient was changed to a maximum effort after a weather delay on 11 July, due to the effectiveness of the reply by the Luftstreitkräfte.

[25] On 7 July, Gough asked for another postponement of five days; some British heavy artillery had been lost to the German counter-bombardment, some had been delayed and bad weather had hampered the programme of counter-battery fire.

After Gough supported Anthoine, Haig reluctantly agreed to wait until 31 July, despite endangering Operation Hush, which had to catch the high tides from 7 to 8 August; a delay might force a postponement for a month.

[29] Patrols from the reserve brigades were to advance towards the red line (fourth objective) 1,000–1,500 yd (910–1,370 m) further on, at the discretion of divisional commanders, if the German defence opposite had collapsed.

[41] I Corps was to form the northern flank of the attack, by crossing the tongue of land between the Yser Canal and the floods at the Martjevaart/St Jansbeek stream as far as Poesele, south of Noordshoote.

Elastic defence, which allowed local withdrawals, was rejected by Fritz von Loßberg, the new 4th Army Chief of Staff, because they would disorganise troops moving forward to counter-attack.

The strong points on the left were quickly suppressed but those on the right held out for longer and caused many casualties, before German infantry sallied from shelters between the front and support lines on the right flank.

The attached battalions of the 53rd Brigade of the 18th (Eastern) Division, moved forward across the Menin road expecting the ground to be undefended and it was not until 9:00 a.m. that the mistake was discovered by the divisional commanders.

Brigadier-General Clifford Coffin decided that it was too late to stop the attack and sent a company of the reserve battalion to fill the gap to the south but this did not prevent German enfilade fire.

As the Scots reached the Steenbeek, machine-gun fire from 60 yd (55 m) beyond the opposite bank caused the cancellation of the plan to form a bridgehead at Maison du Rasta.

[65] In the XIV Corps area, the Guards Division, on the left flank, had crossed the Yser Canal on the afternoon of 27 July after a reconnaissance report from British airmen.

After patrols from the 51st Division pushed northward and found no Germans near Poesele, Anthoine ordered I Corps to advance to a line from the Martjewaart cutting to the Saint-Jansbeek and Broenbeek streams, to create a defensive zone between Drie Grachten and the confluence of the Corverbeek.

Attempts to hold the ground between the black and green lines failed due to the communication breakdown, the speed of the German advance and worsening visibility as the rain increased during the afternoon.

[85] The defensive system was designed to delay an attacker and create the conditions for an encounter battle advantageous to the defenders, not the 4,000 yd (2.3 mi; 3.7 km) advance achieved by XIX and XVIII Corps.

The Germans recaptured St Julien just west of the green line on the XVIII Corps front, where the counter-attack was stopped by mud, artillery and machine-gun fire.

The training of the Fifth Army troops had enabled them to use Lewis guns, rifle grenades, trench mortars and tanks to overwhelm German pillboxes, when the artillery had managed to neutralise the defenders of a sufficient number of blockhouses in advance.

[94] The German defensive success on the Gheluvelt Plateau left the British in the centre open to enfilade-fire from the right, contributing to the greater number of losses incurred after the advance had stopped.

Prior and Wilson wrote that the failure had deeper roots, since successive attacks could only be spasmodic as guns were moved forward, a long process that would only recover the ground lost in 1915.

This was far less than the results Haig had used to justify the offensive, in which great blows would be struck, the German defences would collapse and the British would be able safely to advance beyond the range of supporting artillery to the Passchendaele and Klercken ridges, then towards Roulers, Thourout and the Belgian coast.

[99] Operation Summer Night (Unternehmen Sommernacht) was a German methodical counter-attack (Gegenangriff) near Hollebeke, in the Second Army area on the southern flank, which began at 5:20 a.m. on 5 August.

After a short bombardment, three companies of I Battalion, Infantry Regiment 62 of the 12th Division captured a slight rise 0.62 mi (1 km) north-east of Hollebeke, surprising the British, who fell back 260 ft (80 m).

[103] On 1 August, a German counter-attack on the Fifth Army front, at the boundary of the II and XIX Corps, managed to push back the 8th Division for a short distance south of the Ypres–Roulers railway.

Troops were quickly tired by rain, mud, massed artillery bombardments and lack of food and water; rapid relief of units spread the exhaustion through all the infantry, despite fresh divisions taking over.

Five guns were captured and with the French close to Merckem and over the Steenbeek near St Janshoek, the German defences at Drie Grachten were outflanked from the south and Langemarck made vulnerable to attack from the north-west.