this stage of the war was to switch batteries and HAG headquarters around as required. 44th Siege Battery moved to 23rd HAG on 27 January 1917, then on 3 February it got orders for an immediate move, joining I ANZAC Corps with Fifth Army on 6 February for the Operations on the Ancre, January–March 1917. Next it was with First Army, first with 55th HAG, then from 18 March with 26th HAG. First Army was preparing for its part in the forthcoming Arras Offensive, the attack on Vimy Ridge planned for 9 April. The role of heavy howitzers was clarified in early 1917, when it was recognised that they were best suited for counter-battery (CB) fire against well-protected enemy guns. For Vimy there were dedicated CB groups with observation aircraft, beginning 20 days before the attack (Z minus 20) with systematic fire, then from Z minus 10 switching to more vigorous destruction of all known enemy batteries, telephone exchanges and observation posts. First Army's commander, Gen Henry Horne was himself a gunner and took personal command through his Major-General, Royal Artillery, Maj-Gen H.F. Mercer, of the heaviest 15-inch and 12-inch guns. 26th HAG was firing in direct support of the Canadian Corps attacking on Vimy Ridge itself. The huge weight of artillery, including 'some of the most accurate counter-battery fire of the war', together with the dash of the Canadians ensured the success of the attack. Successes dwindled as the Arras offensive continued, though the guns continued their support. In May 44th SB brought CB fire and direct bombardment onto Mericourt. But CB fire could work both ways: on 28/29 May the battery suffered two men wounded and cartridge dugouts destroyed by enemy guns. Cambrai 44th Siege Battery continued its CB duties from June to October 1917, then between 12 and 18 November it was transported to join 90th HAG with Third Army, preparing for the Battle of Cambrai. The massed guns were kept silent until the surprise attack was launched in 20 November, but their positions and targets were accurately surveyed so that they could fire 'off the map' without need for prior registration. The 'super heavy' artillery group fired concentrations on the villages behind the lines, 44th SB firing on Havrincourt, Flesquières and Graincourt, major objectives for the attack. The attack was a great success, but its exploitation was disappointing. 44th Siege Bty switched to the command of