The mine warfare waged by the French was continued by the British, exploiting the advantage of being on the dip slope and only having to dig horizontally into the ridge to undermine German positions.

Success would gain more defensive depth and forestall mine attacks on the German positions before the British could organise their defences on the ridge.

A British plan to recapture the front positions and take the German side of the ridge was cancelled because of the demand for men and equipment for the forthcoming Battle of the Somme.

British planning continued and became the basis for the much larger attack by the Canadian Corps at the Battle of Vimy Ridge (9–12 April 1917).

[3] A battalion of Reserve Infantry Regiment 229 built fake encampments and made several approach marches to simulate reinforcements to French reconnaissance aircraft.

Unternehmen Rupprecht I began on 23 January, when the 2nd Bavarian Division blew mines and captured several French trenches near Thélus.

At 11:00 a.m. the French bombardment reached the intensity of drumfire (shells exploding in such quick succession that the reports merged into a rumble) and at 1:10 p.m. the Germans were forced to retire.

Further north, in the area of the three great battles of Artois in 1914 and 1915, hostilities had continued and on 8 February, the Germans captured 0.5 mi (0.80 km) of trench south of Central Avenue (Ave).

Where barbed wire had been put out, it was poor and in bad condition; the French positions were good enough for jumping-off lines for another attack but not for defence.

The British resumed hostilities, only to find that their trench parapets were not bulletproof and both sides came into the open to dig better defences under a tacit truce.

The British then found that the superiority of German observation was such, that turning the area into a "windy corner" of the Western Front had backfired; the construction of better defences was much harder than expected.

On Vimy Ridge, the Berthonval and Carency sectors were transferred to IV Corps (Lieutenant-General Henry Wilson) of the First Army, from XVII Corps (Lieutenant-General Sir Julian Byng) of the Third Army and from the 25th Division to the 47th (1/2nd London) Division, which extended its right flank .75 mi (1.21 km) southwards to P sector.

A retirement for 3,000–4,000 yd (1.7–2.3 mi; 2.7–3.7 km), to a defensible line between Ecurie and Souchez, was judged politically impossible, after the great sacrifices made by the French in 1915.

A retirement would also show the Germans that no spring offensive was intended, contrary to Haig's desire that one should be made to appear imminent by mining and trench raiding on the ridge.

When either side sprung a mine, their troops would rush forwards and try to consolidate the near lip as their opponents smothered the area with artillery and machine-gun fire.

Working parties dug in on the forward edge of the craters, assisted by the 105th Field Company RE and the divisional pioneer battalion, at a cost of 107 casualties.

[15][16] In the five weeks before 21 May, the 25th Division (Major-General Beauchamp Doran) suffered 1,270 casualties, although the British miners gradually gained an advantage over their German counterparts.

In the weeks before the German attack, the weather was so bad that reconnaissance flights over the ridge by the Royal Flying Corps (RFC) had been possible on only ten days.

[19] Loringhoven used his influence at OHL to mass eighty artillery batteries for the operation on the 4 mi (6.4 km) of front from Liévin, a suburb of Lens, to Vimy, carefully hidden between houses and in buildings.

In the smoke and dust the German infantry got half-way across no man's land before the British could see them, moving in skirmish lines, the men 3 yd (2.7 m) apart.

Small British parties attempted to make hasty counter-attacks but until the German bombardment slackened around 10:00 p.m. British headquarters remained ignorant of the situation on the ridge; the commander of the 141st Brigade, Brigadier-General William Thwaites, was in Zouave Valley when the German bombardment began and managed to contact the 47th (1/2nd London) Division HQ.

The Germans had great difficulty consolidating their new positions, in the dark, under artillery-fire and counter-attack; in the 8th Company area, the troops formed a human chain to pass hand-grenades forward.

[27] On 23 May the weather was still too hazy but artillery-observation aircraft took off at 3:30 a.m.;before conditions got worse, a reconnaissance on the First Army front found suspicious rail movements at Lens.

Communication with the rear was cut but a wireless stayed operational for long enough to inform the 99th Brigade and a liaison officer was sent to the 22nd Battalion, Royal Fusiliers on left flank and runners went forward immediately.

[31] Haig thought that IV Corps had bungled and that a counter-attack big enough to ensure success would need another 40 British heavy artillery batteries.

Although the Germans had gained observation over the British lines, they had not become untenable and Haig decided that the diversionary Attack on the Gommecourt Salient north of the Somme, was more important.

[33] Rupprecht was pleased about the large bag of prisoners (229) who were questioned by German interrogators and gave away much information on the orders of battle of the 47th (1/2nd London) and the 25th divisions, artillery-observation officer working methods, details about machine-guns and field fortifications.

[34] In the first 1916 volume of the History of the Great War (1932), the official historian, James Edmonds, wrote that the Germans judged Unternehmen Schleswig-Holstein a complete success.

Reserve Infantry Regiment 86 reported that there had been little British resistance but the other battalions noted hand-to-hand fighting and enfilade fire from the flanks.

The German infantry fired green flares to get the artillery to increase the range but this gave away the line, which the British then subjected to massed heavy artillery-fire.