John Mackay was born in Strathen Skerray son of George Mackay and Christina Mackay he was a brother of Thomas N Mackay who also appears on Skerray War Memorial.

He served for 5 years in the Royal Naval Reserve and then enlisted at Morphettville, South Australia on the 3rd September 1914 serving with the 12th Battalion AIF, he was 35years of age. On enlistment he listed his next of kin as his brother Tom (Thomas) Mackay this was changed on Thomas's death to his brother Hector (See Skerray Roll of Honour for World War 1).

The 12th Battalion was one of the first infantry units raised for the AIF during the First World War. Half of the battalion was recruited in Tasmania, the other half was recruited in South Australia, and Western Australia. With the 9th, 10th and 11th Battalions it formed the 3rd Brigade of the Australian Imperial Force.

The battalion was raised within three weeks of the outbreak of war in August 1914 and embarked two months later. After a brief stop in Albany, Western Australia, the battalion proceeded to Egypt, arriving in early December. The 3rd Brigade was part of the ANZAC landing on the Gallipoli Peninsula on 25 April 1915 and was the first ashore at around 4:30 am. The battalion was heavily involved in establishing and defending the front line of the ANZAC positions at ANZAC Cove.

Private John Mackay was listed as missing in action on the 25th of April1915 and his death as being killed in action was confirmed by a court of inquiry on 5th June 1916.

John Mackay was the brother of Thomas N Mackay who was killed in action serving with the Seaforth Hihlanders. He also had 3 other brothers Hector, George and Donald. He also had 2 sisters Janet and Annie