Born in Albion Mines (now called Stellarton), Pictou County, Nova Scotia, "Pete", as he was known, lived most of his life in Medicine Hat with his mother.

When his platoon was held up by uncut wire and a machine gun causing many casualties, Pte.

He inflicted many more casualties among the enemy, and then carrying the captured machine gun, he led his platoon to the final objective.

Robertson’s most determined use of the machine gun kept down the fire of the enemy snipers; his courage and his coolness cheered his comrades and inspired them to the finest efforts.

(London Gazette, no.30471, 11 January 1918) [3] Robertson is buried at Tyne Cot Cemetery, Passchendaele, Belgium, located 5 miles north east of Ypres.