[1] Cook sailed to India in late 1861 at the age of eighteen, joining the British Indian Army, Bengal Staff Corps as an ensign before being promoted lieutenant on 29 March 1862,[2] and soon after his arrival was posted to the 3rd Sikh Infantry.

At dawn, as the Afghans fled their positions, Cook collected a few men and charged and killed a large number of enemy who were trying to rescue one of their guns before going to the aide of Major Galbraith.

[9][10] Just days after the action, Major Galbraith wrote to General Roberts a report dated 'Camp near Zabbardast Kila, 5 December 1878:[8][11] I have the honour to submit the following statement in the hope that should you see fit you will bring the name of Captain Cook, 5th Goorkha Regiment, to the favourable notice of His Excellency the Commander-in-Chief.

"On the morning of the 2nd December 1878, after our troops had stormed the second entrenchment above the "Spin Gawai", the enemy attempted to rally in the woods at our right flank, and at the same moment about 150 to 200 men were observed moving down from a height on the left.

I had seen him advancing but thought him a friendly sepoy, until he raised his rifle at about three yards from me, fortunately an intervening tree sheltered me for the moment, and gave me time to turn and discharge my pistol at him without effect.

The whole affair was the work of [a moment] but I feel convinced that but for Captain Cook's prompt endeavour to draw the man's fire upon himself, I should, in all probability, have been shot before I could have again discharged my pistol, several others of the enemy were at the time within a few yards of us.

"[8]He was 35 years old, and a captain in the Bengal Staff Corps, British Indian Army, and 5th Gurkha Rifles during the Second Anglo-Afghan War when the following deed took place for which he was awarded the VC: For a signal act of valour at the action of the Peiwar Kotal on the 2nd December, 1878, in having, during a very heavy, fire, charged out of the entrenchments with such impetuosity that the enemy broke and fled, when, perceiving, at the close of the melee, the danger of Major Galbraith, Assistant Adjutant-General, Kurum Column Field Force, who was in personal conflict with an Afghan soldier, Captain Cook distracted his attention to himself, and aiming a sword cut which the Douranee avoided, sprang upon him, and, grasping his throat, grappled with him.