The Battle of Arras was a British offensive on the Western Front during the First World War. From 9 April to 16 May 1917, British troops attacked German defences near the French city of Arras on the Western Front. The British achieved the longest advance since trench warfare had begun, surpassing the record set by the French Sixth Army on 1 July 1916. The British advance slowed in the next few days and the German defence recovered. The battle became a costly stalemate for both sides and by the end of the battle, the British Third Army and the First Army had suffered about 160,000 casualties and the German 6th Army about 125,000.

The Fifth Army was a field army of the British Army during World War I that formed part of the British Expeditionary Force on the Western Front between 1916 and 1918. The army originated as the Reserve Corps during the preparations for the British part of the Somme Offensive of 1916, was renamed Reserve Army when it was expanded and became the Fifth Army in October 1916.