From 1914, enlistment in the Australian Imperial Force (AIF) was restricted to volunteers but from mid-1916 encouraging enough eligible recruits became increasingly difficult.

Australian Prime Minister Billy Hughes came under sustained pressure from Britain's War Council to follow Britain and New Zealand in introducing conscription.

In August 1916, Hughes said voluntary recruiting could not be relied on to maintain Australian forces at full strength.

Appealing to "the patriotism of Australian manhood," Hughes said: "The great offensive ??? has cost a fearful price, yet it must be pressed forward with implacable resolution. To falter now is to make the great sacrifice of lives of no avail."

The eight-week conscription campaign split communities. It was conducted during the Battle of the Somme in France, which historian Joan Beaumont says infused the debate "with the passion and hysteria of mass grief."

The first referendum on October 28, 1916, saw conscription defeated with 1,087,557 in favour (48.4 per cent) and 1,160,033 against (51.6 per cent).

In 1917, as the carnage in France and Belgium grew, and the US and Canada introduced conscription, Hughes called another vote for December 20, claiming 7000 recruits a month were needed.

By this time, Hughes had walked out on the Labor Party, joined with the Liberals to form the Nationalist Party, won a May election and incurred the wrath of the working class by smashing a national strike.

The second referendum, held amid tightened censorship, was again divisive politically and socially with Melbourne's Irish-born Catholic Archbishop Daniel Mannix a vehement 'no' campaigner.

In December, Australia voted "no" again, by a wider margin of 94,000 votes. Soldiers were split too, voting "yes" 103,789 and "no" 93,910.

The AIF remained a voluntary force and Joan Beaumont says this fuelled the myth of the Australian soldier as the citizen in arms - "not a professional soldier but a natural fighter."

By war's end, about 420,000 Australians had enlisted - 38.7 per cent of males aged 18 to 44.

Initially, eligible men had to be 19 to 38 years and at least 5ft 6in (168cm) to enlist. A third of all volunteers were rejected in the first year, many with defective teeth.

As the war progressed, and the need for new recruits increased, recruitment standards relaxed. By June 1915, they could be aged 18 to 45 and by 1917, the minimum height had fallen to just 5ft (152cm).

The 1st-4th AIF Battalions were raised in NSW and the 5th-8th Battalions from Victoria within a fortnight of the declaration of war.

The 9th came from Queensland, the 10th from SA, the 11th from WA and the 12th was largely Tasmanian.

All up, 60 AIF Battalions were raised and saw active service.

Later in the war, 16 new battalions were created comprising veterans of severely-depleted battalions and newly-arrived recruits.

Once the reports of losses at Gallipoli hit home, 152 Victorians enlisted as "The Fair Dinkums" and sailed away in August 1915.

By December 1915, 52 per cent of the Australian Army had enlisted.

Spurred on by recruitment posters, some from artist Norman Lindsay, a series of nine 'snowball' marches from late in 1915 gathered men along country roads to recruitment camps.

In NSW, they included the Coo-ees from Gilgandra, the Wallabies from Walgett, the Men from Snowy River from Delegate, the Waratahs from Nowra and the Kangaroos from Wagga Wagga. Queensland's Dungarees marched 270km from Warwick to Brisbane.

Military historian Dr Peter Stanley says: "The snowball marches have been celebrated ??? as the epitome of voluntarism. In fact, they represented the failure of voluntary enlistment."

In cities and country towns alike, pro-enlistment urging was blunt.

A huge sign trumpeting "Enlist The Empire Calls" in Sydney's George Street was unavoidable while volunteers leaving Tumut passed by a banner held by women that read "If you won't go we will".

Author John McQuilton says irresistible pressure was brought to bear on 'eligibles' in north-eastern Victoria but once rural communities "were satisfied that their eligibles had gone, they resisted any further attempts to force the remaining men to enlist."

A 1977 survey of veterans found motives for joining up ranged from patriotism, a sense of duty, social pressure, spirit of adventure, self-interest and "hatred of the Hun".

The Road to Remembrance is published by Fairfax Media in partnership with the Department of Veterans' Affairs.