The Battle of Arras was a British offensive on the Western Front during World War I. 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 and First Army had suffered about 160,000 casualties and the German 6th Army about 125,000.
For much of the war, the opposing armies on the Western Front were at stalemate, with a continuous line of trenches from the Belgian coast to the Swiss border. The Allied objective from early 1915 was to break through the German defences into the open ground beyond and engage the numerically inferior German Army in a war of movement. The British attack at Arras was part of the French Nivelle Offensive, the main part of which was the Second Battle of the Aisne 50 miles to the south.