By Mike McCarthy, North of England Correspondent
Hundreds of events are taking place across Britain to remember the "Pals" - groups of friends, neighbours or colleagues who joined up to form their own battalions in World War One.
A century on exhibitions, concerts and church services are being held in memory of those who joined up to defend their country in what became a highly controversial recruitment campaign.
In towns and cities across the country thousands of men responded to a national appeal by Lord Kitchener, the then-Secretary of State for War.
He believed potential soldiers would be more likely to enlist if they knew they would probably be fighting alongside friends.
It was hailed as a huge success with the majority of recruits in the first few years of war made up of "Pals" battalions.
But heavy casualties led to huge losses in some towns or individual industries.
A banner has been erected in Accrington to remember the 'Pals'Even today, some areas of the country remain shaped by the sudden loss of so many men within relatively small communities.
One of the best known "Pals" battalions was recruited in and around the hilly Lancashire town of Accrington.
Cath Holmes' great-uncle Walter joined up with the original Accrington Pals in 1914. He ended up at Ypres in Belgium where he died in September 1918.
He was one of hundreds to die from the same battalion, whose proper name was 11th (Service) Battalion (Accrington), East Lancashire Regiment.
A banner has recently been stretched alongside Accrington's town hall in memory of the area's "Pals".
Cath's voice wavered and tears formed as she recalled seeing a post about it on Facebook.
"I saw a picture of it being part-way up, so I just ran when I saw it all the way into town just to come and have a look at it," she said.
"I am really proud. I just stood there crying."
The Lancashire town of Accrington was shaped by the loss of so many menLocal historian Helen Barrett told Sky News: "At the end of the war there were so many widows, so many women who'd lost their husbands, brothers, fiancees, friends, cousins.
"There was barely a street that remained untouched. Almost every street had houses where the blinds were drawn as a mark of respect.
"The widows had very little money to live off and had to suffer the indignities of means tests in order to get some money to bring their families up. It was a terrible time for them."
Untold numbers who had enlisted together in a war expected to last just a matter of months died together in a conflict which continued for four years.
Men had marched through their communities in glory as they headed towards what became the slaughter of battle.
Conscription was introduced in 1916. The idea of Britons fighting together as a community of "Pals" became associated with overwhelming and disproportionate bloodshed. It has never been repeated.