The sleepy plains and chalky ridges east of Arras, France, where thousands of Canadians fought and died 100 years ago, may seem a world away from the politics of Ottawa, but it wasn't on Sunday.

Prime ministers, presidents, princes, soldiers, schoolchildren and descendents of those who fought at Vimy Ridge gathered at the foot of the country's soaring memorial to mark the centennial since the sacrifice.

Back home, however, some veterans of subsequent wars took to social media to express their frustration the Liberal government has yet to live up to a key 2015 campaign promise of returning them to a system of lifetime pensions, as opposed to lump sum payments.

A class-action lawsuit brought by former soldiers claims they are being discriminated against because the current system is not as generous as the one set up for troops who returned from Vimy and the First World War. (Murray Brewster/CBC News)

"I find it ironic that they're celebrating the Battle of Vimy Ridge when they're also fighting veterans in court," Glen Kirkland, a former corporal wounded in Kandahar in 2008, said in an interview with CBC News from his home in Manitoba.

He is referring a class-action lawsuit brought by former soldiers from the Afghanistan War, who claim they are being discriminated against because the current system is not as generous as the one set up for troops who returned from Vimy and the First World War.

"They've made promises and they're not living up to them. They have to bring back the pension," said Kirkland. "What better way to honour the sacrifices of Vimy than to actually look after the veterans of today."

The Liberals made a return to the lifetime system of pensions one of their signature promises of the 2015 election and last month's federal budget re-iterated that pledge but did not put any money behind it — for the moment.

Canadian Prime Minister Justin Trudeau, left, Britain's Prince William, centre, and Prince Harry stand during the commemorations. Last year, Trudeau's government poured $5.7 billion into better veterans benefits and care. (Philippe Huguen/Associated Press)

The government is promising some sort of announcement later this year, but officials, who spoke on background after the budget was released, said the plan would not meet the demand from some veterans' groups for equality with the old pension act system.

Last year, Prime Minister Justin Trudeau's government poured $5.7 billion into better veterans benefits and care. In the latest budget, tabled last month, $600 million more — a lot of it on education.

There was also a top-up of the controversial lump sum payment that Kirkland and others want to see replaced.

There was a reminder Sunday that Canada is not the only country facing frustrated veterans from modern wars.

"We have all tried to improve what we do for veterans in different ways," said Michael Fallon, the British defence secretary.

In the U.K., much like Canada, homelessness among ex-soldiers and mental health service needs are among the major issues of public policy debate.

"We need to keep thinking as governments as to how we organize that help and make sure those who need it can get it," Fallon told CBC News.

British Defence Secretary Michael Fallon says in the U.K., much like Canada, homelessness among ex-soldiers and mental health service needs are among the major issues of public policy debate. (Murray Brewster/CBC News)

Trudeau's speech on Sunday was long on the symbolism, sacrifice and values. He quoted from the letter of soldier Pte. William Henry Bell, a 20-year-old killed at Vimy, who wrote home to his parents two days before the battle.

The simple of message of home, family and comfort resonated for Trudeau, who held it up as an example of dignity in the face of fate.

"Friends and honoured guests, let us hold to the grace of William Henry Bell. To the grace of the ones who stood by their friends, through unimaginable hardship. Through death itself," he told the thousands who gathered on the green slopes.

The soldiers who fought and died there "were Canadians. They were valiant, beyond measure."

Trudeau also used it as an appeal for peace, coming as it did amid rising tension with Russia following the volley of cruise missiles fired by the U.S. into Syria.

"As I see the faces gathered here – veterans, soldiers, caregivers, so many young people – I can't help but feel a torch is being passed," Trudeau said. "One hundred years later, we must say this, together. And we must believe it: Never again."