day were the worst in the history of the British army, with 57,470 British casualties, 19,240 of whom were killed.
British survivors of the battle had gained experience and the BEF learned how to conduct the mass industrial warfare, which the continental armies had been fighting since 1914. The continental powers had begun the war with trained armies of regulars and reservists, which were wasting assets. Crown Prince Rupprecht of Bavaria wrote, "What remained of the old first-class peace-trained German infantry had been expended on the battlefield". A war of attrition was a logical strategy for Britain against Germany, which was also at war with France and Russia. A school of thought holds that the Battle of the Somme placed unprecedented strain on the German army and that after the battle it was unable to replace casualties like-for-like, which reduced it to a militia.
The destruction of German units in battle was made worse by lack of rest. British and French aircraft and long-range guns reached well behind the front-line, where trench-digging and other work meant that troops returned to the line exhausted. Despite the strategic predicament of the German army, it survived the battle, withstood the pressure of the Brusilov Offensive, and conducted an invasion of Romania. In 1917, the German army in the west survived the large British and French offensives of the Nivelle Offensive and the Third Battle of Ypres, though at great cost.
Falkenhayn was sacked and replaced by Hindenburg and Ludendorff at the end of August 1916. At a conference at Cambrai on 5 September, a decision was taken to build a new defensive line well behind the Somme front. The Siegfriedstellung was to be built from Arras to St. Quentin, La Fère and Condé, with another new line between Verdun and Pont-à-Mousson. These lines were intended to limit any Allied breakthrough and to allow the German army to withdraw if attacked; work began on the Siegfriedstellung (Hindenburg Line) at the end of September. Withdrawing to the new line was not an easy decision and the German high command struggled over it during the winter of 1916–1917. Some members wanted to take a shorter step back, to a line between Arras and Sailly, while the First and Second army commanders wanted to stay on the Somme. Generalleutnant von Fuchs on 20 January 1917 said that,
Enemy superiority is so great that we are not in a position either to fix their forces in position or to prevent them from launching an offensive elsewhere. We just do not have the troops.... We cannot prevail in a second battle of the Somme with our men; they cannot achieve that any more. (20 January 1917)
— Hermann von Kuhl
and that half measures were futile, retreating to the Siegfriedstellung was unavoidable. After the loss of a considerable amount of ground around the Ancre valley to the British Fifth Army in February 1917, the German armies on the Somme were ordered on 14 February, to withdraw to reserve lines closer to Bapaume. A further retirement to the Hindenburg Line (Siegfriedstellung) in Operation Alberich began on 16 March 1917, despite the new line being unfinished and poorly sited in some places.
The British and French had advanced about 6 miles (9.7 km) on the Somme, on a front of 16 miles (26 km) at a cost of 419,654 British and 202,567 French casualties, against 465,181 German casualties. Until the 1930s the dominant view of the battle in English-language writing, was that the battle was a hard-fought victory against a brave, experienced and well-led opponent. Winston Churchill had objected to the way the battle was being fought in August 1916, Lloyd George when Prime Minister criticised attrition warfare frequently and condemned the battle in his post-war memoirs. In the 1930s a new orthodoxy of "mud, blood and futility" emerged and gained more emphasis in the 1960s when the 50th anniversaries of the Great War battles were commemorated.
The Battle of the Somme was one of the costliest battles of the First World War. The original Allied estimate of casualties on the Somme, made at the Chantilly Confe