Anzac Day started in Sydney with reflections of the Western Front.

Addressing the pre-dawn service at Martin Place, Major General Peter "Gus" Gilmore, recalled the journey made by Australian troops in 1916. Having fought at Gallipoli the year before, in 1916 they were making their way to northern France.

"The monotonous rattle of the rail tracks must have served some distraction," said Major General Gilmore, "as they travelled north through the glorious French countryside 100 years ago today."

On the Western Front, they were issued steel helmets and gas marks for the first time. And, within a few months, they were engaged in the Battle for Fromelles. There they suffered the heaviest one-day casualty in Australian military history: 5533 men in 24 hours.

"If they were here with us today, just as the person right next to you stands this morning," said Major General Gilmore. "Straight of limb, true of eye, steady and aglow, could you, could I, could we Australians all look them in the eye and confidently say we carry their torch high?"

Major General Gilmore thought the answer would be in the affirmative. "I have no doubt that we carry their torch high," he said.

But if recollections of the First World War were a dominant theme of services on Monday, the dominant aspect of the marches was surely the human reminders of the Second.

According to Mr Jourdain, about 2800 troops had served in his 2/33 Australian Infantry Battalion.

But only one other walked alongside him on Monday.

"This is about remembrance," said Mr Jourdain. "It isn't about the glory or anything like, it is all about the remembrance of the people that didn't come back."

For Russ Green, 93, Doug Spinney, 95, and Fred Chivers, 94, this would be their last march underneath the banner of their 2/6 Australian Armoured Regiment.

"This is the last march," said Mr Green. "We hand the flag in today."

Mindful of the passage of time, they have donated their banner to the Army Tank Museum at Puckapunyal.

There were 16,824 march participants in Sydney on Monday.

Ron Dixon, 94, and Bill Coffey, 93, were the lone surviving veterans of the 2/5 Field Regiment who marched.

"But we have the sons and ex-servicemen and the daughters," said Mr Dixon. "They're all marching with us," he said.

Herbert Neasby, meanwhile, had more than the usual compliment of relatives marching with him. The veteran of the 2/1 Pioneer Battalion marched on Monday with another three generations of his family: sons Mark and Greg, grandchildren Natalie and Catherine, and great-grandson Oliver.

Rod White, the NSW President of the RSL, said Monday's were historic commemorations. "We are actually witnessing the passing of the baton," he said.

"There will be too few World War Two veterans. We owe so much to that generation for getting us through the Second World War and building this nation in the 1950s and 60s."