As the first world war broke out, Britain's army was well trained but small. Its 100,000 soldiers were nowhere near enough to take on the might of the forces it opposed.
Lord Kitchener, the Minister for War, came up with a solution. He didn't want to enforce conscription, so he mounted a massive publicity campaign, encouraging groups of friends and colleagues to sign up and fight together.
They'd be more willing to lay their lives on the line, he deduced, if they were serving alongside people they knew.
It was a spectacular success. Recruiting offices were swamped with volunteers, eager to join the new "pals battalions".
Their training was limited and basic, certainly by modern standards, but what these friends lacked in expertise, they more than made up for in esprit de corps.
In many British cities, crowds waved these bands of brothers off to battle. But in Edinburgh, there was huge admiration for one particular group.
Sir George McCrae, a local businessman and former MP, had persuaded players from Heart of Midlothian football club to join the 16th Battalion, the Royal Scots. They were young, athletic and eager, just what he needed. But, more importantly, they were local celebrities. He was sure their example would encourage others to follow.
His plan worked. He took the players to a rally at a concert hall in Edinburgh's city centre. Inspired by their example, hundreds of young men marched straight from the venue to a recruiting office nearby and signed up.
Within days McCrae had the fighting force he needed. Players and fans from across the city and beyond had volunteered to go to war.
Many among McCrae's battalion were famous before they left, but on the first day of the Somme they earned a new reputation, achieving more amid the carnage of that single day than any other fighting force in the British army.
The war took its toll on Hearts. Sixteen members of the first team went off to battle. They were the best team in Scotland when the conflict broke out, but seven died in action, two more succumbed to the effects of gassing and a tenth was crippled in the fighting and never played again.
A cenotaph to the club's sacrifice was erected in central Edinburgh shortly after the end of the conflict and a memorial cairn has now been erected in Contalmaison, the French village McCrae's battalion helped to liberate.
Their story, which lay dormant for generations as Britain moved on after the war, is now being retold with pride and passion by the club's supporters. They're determined the sacrifice shouldn't be forgotten, and nor should the debt we still owe to those brave players and fans today.