Samuel McMullan was born on 4th March 1892 in Magherafelt, County Londonderry. His address in the 1901 Census of Ireland, when he was 9 years old, was 42 Ballinahone More, Tobermore, Co. Londonderry. By the time of the 1911 Census his family had moved to 20 Gotha Street, Belfast. He was 19 years old.

Sam joined the Army in August 1914. He became part of a Regiment named the 6th Battalion, Royal Inniskilling Fusiliers.

 After training Sam and his Regiment were sent to Bulgaria. They arrived on 11th July 1915. After that they went to Suvla Bay, Gallipoli, Turkey, arriving on 7 August 1915.

They later went on to fight in Palestine.

On 2nd May 1918 Sam’s Regiment was sent to France. Sam was killed in action on 3rd October 1918 at a village named Gouy, Le Catelet, France.

He was 26 years old. A book about the 6th Battalion, Royal Inniskilling Fusiliers was written after the war. Sam is mentioned in this book: "It is invidious to single out any particular soldier for special mention, but this story of the part played by the 6th Battalion Royal Inniskilling Fusiliers in the Great War would not be complete without a word of praise for Private Samuel McMullan, whose deeds in action on October 3, at Prospect Hill, will ever live so long as there remains alive one man who saw them, and whose grave is there now."