On 24th March 1915, French Commander-in-Chief Joffre enquired of Sir John French whether the
British Expeditionary Force would be ready to co-operate in an offensive which would take place
5-6 weeks later. Having received a positive reply from the British commander, he issued initial
details on 6th April : “In the last day of April, the French 10th Army, acting in concert with the
British First Army, will undertake an important attack north of Arras with a view to piercing the
enemy’s line”.
Details of operational planning were placed in the hands of Sir Douglas Haig’s First Army. Neither
this, nor the overall strategic plan, was notably affected by the German gas attack north of Ypres on
22nd April, with the exception of various units of First Army being moved and placed on standby to
move to Ypres. Indeed, Allied resolve was strengthened with the sinking of the Lusitania on the 7th
May. Plans began to take shape, and units began to move into position from early April. The British
attack at Gallipoli was launched on 25th April 1915, opening another front and placing an
additional and growing demand on already stretched military resources.
On 2nd May, French was informed that the main attack would now take place on 7th May. The
First Army had five days to complete their preparations. Heavy rain on 6th May and dense mist on
7th May caused a French postponement of the main attack: it would now go in on 9th May – and
the subsidiary attacks would happen at the same time, not a day later as in accordance with the
original strategy. 9th May was a fine sunny day.
Ammunition shortage had been problematic since the opening stages of the War and was by now
particularly acute. There were a total of 504 field guns and 121 heavies in the First Army, but
problems with many of them. A small mobile force of mounted and cyclist troops with a section of
a mountain battery of artillery, were also ready to moved. Three squadrons of 1st Wing Royal
Flying Corp spent four days doing reconnaissance.