On 13 March 1917, 126th Hvy Bty was ordered to 31st HAG with First Army, which it joined on 21 March. Here it formed part of the counter-battery support for I Corps in the Battle of Vimy Ridge. The corps' objective was Bois en Hache, north of the Ridge. There was a 48-hour preliminary bombardment, then when the attack went in at 05.30 on 9 April the most powerful and concentrated bombardment of the war so far crashed onto the German lines. The role of the 'heavies' was to bombard targets in depth and carry out a comprehensive CB fireplan. The attack was a great success.