[3] Commanding the 119th Battery, Royal Field Artillery, Alexander was awarded the Victoria Cross (VC) for gallantry on 24 August, during the action of Elouges.

When the flank guard was attacked by a German corps, Alexander handled his battery against overwhelming odds with such conspicuous success that all his guns were saved notwithstanding that they had to be withdrawn by hand by himself and volunteers led by a Captain (Francis Octavius Grenfell) of the 9th Lancers.

[8][12][13] Towards the start of 1916 he was appointed Brigadier General Royal Artillery to XV Corps, a unit which played a large role in the First day on the Somme.

Alexander laid down effective artillery barrages as XV Corps advanced, playing a large part in the success of its attacks at Fricourt and Mametz.

[14] The military historian, Brigadier-General Sir James Edmonds, was so impressed by Alexander's techniques that he reproduced full plans of his barrages in the History of the Great War.

Alexander continued to develop his creeping barrages which proved pivotal in XV Corps' victory at the Battle of Bazentin Ridge on 14 July.