The Battle of Arras (also known as the Second Battle of Arras) was a British offensive on the Western Front during World War I

Arras 1917

The Battle of Arras (also known as the Second 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 5th, 9th, 12th and 16th  Lancers were brought up to the front, the 12th leading, in readiness for the expected breakthrough. The weather was bitterly cold with snow on the night of the 9th April and several horses of the 12th died of exposure and many men were frostbitten. After being shelled and machine gunned the 12th were withdrawn to Wailly on the 10th April. For the cavalry the Battle of Arras was over. 

 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 armies had suffered about 160,000 casualties and the German 6th Army 125,000 casualties.

For much of the war, the opposing armies on the Western Front were at a 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 (Westheer) in a war of movementThe British attack at Arras was part of the French Nivelle Offensive, the main part of which was to take place on the Aisne 50 miles (80 km) to the south.

 The aim of the French offensive was to break through the German defences in forty-eight hours. At Arras the British were to re-capture Vimy Ridge, dominating the plain of Douai to the east, advance towards Cambrai and divert German reserves from the French front.

The British effort was a relatively broad front assault between Vimy in the north-west and Bullecourt to the south-east. 

After a long preparatory bombardment, the Canadian Corps of the First Army in the north fought the Battle of Vimy Ridge and took the ridge. The Third Army in the centre advanced astride the Scarpe River and in the south, the Fifth Army attacked the Hindenburg Line (Siegfriedstellung) but was frustrated by the defence in depth and made few gains. The British armies then engaged in a series of small-scale operations to consolidate the new positions. 

Although these battles were generally successful in achieving limited aims, they were costly successes.

When the battle officially ended on 16 May, British Empire troops had made significant advances but had been unable to achieve a breakthrough. 

New tactics and the equipment to exploit them had been used, showing that the British had absorbed the lessons of the Battle of the Somme and could mount set-piece attacks against fortified field defences. After the Second Battle of Bullecourt (3–17 May), the Arras sector then returned to the stalemate that typified most of the war on the Western Front, except for attacks on the Hindenburg Line and around Lens, culminating in the Canadian Battle of Hill 70 (15–25 August).

Four of the Royal Lancers fine predecessor Regiments won battle honours in this campaign:

5th Royal Irish Lancers, 9th Queen's Royal Lancers, 12th Royal Lancers (Prince of Wales's) and 16th The Queens' Lancers.