THE Battle of the Somme, which began 90 years ago this Saturday on 1 July 1916, was one of the blackest days in the history of the British army - and of the city of Edinburgh, whose citizens were killed or wounded in greater numbers than on any single day since Flodden, more than four centuries earlier.
Among the casualties from the capital were members of the 16th Royal Scots, known as McCrae's Battalion, a body also known as the Sporting Battalion because of the number of players and supporters in its ranks.
The story of McCrae's Battalion has been told in the book of the same name by Jack Alexander. Tonight, the tale is retold as a TV documentary, Supreme Sacrifice.
The best-known aspect of the story - indeed, the only aspect that figured in the public consciousness before Alexander's research began to unearth far greater detail - is the involvement of many Hearts players. Their decision to enlist came at a time when they were top of the league, unbeaten in their first eight games, and with an excellent chance of winning the Scottish championship.
While acknowledging the existence in the battalion of players and fans from Hibs and several Fife clubs, Supreme Sacrifice highlights, above all, the impact on Hearts of McCrae's appeal to the people of Edinburgh to join up. It would be a long time from their enlistment in 1914 until players such as Pat Crossan and Duncan Currie saw action in France, but the effect on the team was immediate: overnight route marches and inoculations took their toll, and slowly the club's hopes of the title diminished. Eventually, they were overtaken by Celtic, from whose ranks only one reserve player had joined up.
By the time the war was over, seven Hearts men were dead, and several others were too gravely injured to play again. A few, such as Crossan, did resume their careers, but the side so painstakingly built by the manager John McCartney was no more, and it would take decades before the club was in a position to challenge for honours again.
McCrae himself was a little-remembered figure until the publication of Alexander's work, but in his day he was immensely popular. When he died in 1928, his funeral procession was attended by an estimated 150,000 people, a figure which may not have been exceeded in Scotland since.
Much of the detail of Supreme Sacrifice will be known to those who have read McCrae's Battalion, and in only an hour it cannot pretend to provide more than sketch of what happened from the time the men enlisted to the moment they walked out into No Man's Land and the German machine guns opened up. Viewed as an illustrated companion to McCrae's Battalion rather than a televised alternative version, however, it comes close to being an unqualified success.
Alexander himself is the programme's key interviewee - and rightly so, for without the 16 years of work he put into the story, many details would by now be lost for ever, having died with the battalion's last veterans. Bob Crampsey and Stuart Cosgrove provide some footballing context for the documentary, assessing just how good that Hearts team was, for those few fleeting months in 1914.
• Supreme Sacrifice is on BBC2 Scotland tonight at 9pm.