After graduating from the Royal Military College, Duntroon, in 1939 he served in the Middle East and New Guinea during the Second World War.

[1] The youngest son of Robert Jackson, a professional soldier, and his wife Edith Marguerite (née Vautin); his siblings included an older brother born in 1915 in Surrey, England, and a sister.

[2] With the outbreak of the First World War Jackson's father had joined the Australian Imperial Force (AIF) in November 1914, embarking as adjutant of the 10th Light Horse Regiment.

[2] He subsequently attended a number of schools, completing his secondary education at Scotch College, Melbourne in 1936, where he was a member of the athletics and rugby teams.

[6] His older brother, Donald, was also a professional soldier, having entered the Royal Military College, Duntroon in 1934 and later also reached the rank of brigadier.

[2] After completing his own training at Duntroon, Jackson graduated into the infantry as a lieutenant in December 1939, following the outbreak of the Second World War two months earlier.

[6] Transferring to the 2nd AIF for overseas service, in July 1940 he took up his first appointment commanding a platoon in the 2/25th Battalion where he saw action in the Middle East in North Africa and Syria.

[6] Based in Phuoc Tuy Province, South Vietnam, 1 ATF was involved in counter-insurgency operations against the Viet Cong.

During his period in command the task force was successfully established at Nui Dat, clearing a security zone around the base and conducting offensive operations to the edge of the Tactical Area of Responsibility, while a number of significant actions were fought, including the Battle of Long Tan, which established 1 ATF's dominance over the province.