Born in a suburb of Newcastle, New South Wales, Jeffries was employed as a surveyor at a mining company where his father served as general manager.

Joining a militia battalion in 1912, he was commissioned as a second lieutenant upon the outbreak of war and tasked with the instruction of volunteers for the newly raised Australian Imperial Force.

[2] Apprenticed as a mining surveyor at the Abermain Collieries on the state's northern coalfields, where his father was general manager,[1] Jeffries was noted as a cricketer and a keen horseman who took a particular interest in breeding thoroughbreds.

[3] In July 1912, Jeffries joined the 14th (Hunter River) Infantry Regiment, Citizens Military Force, as a private under the compulsory training scheme.

By this time he was in charge of the survey department at the Abermain Collieries, but was mobilised for home defence duties and the instruction of volunteers for the newly raised Australian Imperial Force at Newcastle and Liverpool camps.

Jeffries commanded B Company during the attack, which he halted at the entrance to Broodseinde railway cutting, as many of the direction tapes leading to the starting position had been destroyed or swallowed up by the mud.

[7] At the designated time of 05:25, the British opened up with an artillery barrage on the German positions just as the Australian forces entered no man's land for the attack.

Heavy machine gun fire assaulted the troops from all directions as they bunched together on the firmer ground to avoid sinking in the boggy mud.

Serious resistance was encountered at Hilside Farm, a strong point to the east of Augustus Wood in the centre of the highest part of the Passchendaele ridge.

The fire from these machine guns forced the men of the 34th Battalion to seek cover on the exposed crest and threatened to halt the entire advance.

[8] Jeffries, realising his force was suffering heavy casualties, quickly organised a bombing party of fourteen men and set about outflanking the pillboxes.

Almost immediately, they came under heavy fire from a pillbox close by a railway embankment, at which time Major J.B. Buchanan, the senior brigade officer with the advance party, fell dead, leaving Jeffries to assume control.

Realising that an attack was imminent, the machine gunner switched around, mortally wounding Jeffries in the stomach and sending the rest of the party to ground.

[9] With the second objective only partially captured, the remnants of the 9th Brigade, battered by artillery and machine gun fire, were forced to relinquish their position and retreat back to their own lines.