July 1st is the anniversary of the beginning of the Battle of the Somme.
Quoting John Derbyshire,
"...the bloodiest day in the history of the British Army. They took 60,000 casualties, of whom nearly twenty thousand were killed.
The Tommies were to get out of their trenches and advance across No Man's Land towards the enemy trenches. This maneuver was to be preceded by an artillery barrage on the enemy lines."
From The Great War and Modern Memory by Paul Fussell:
B.H. Liddell Hart, who was in the 9th Battalion of the King's Own Yorkshire Light Infantry, explains. Just before the Somme attack, "the officers assembled in the headquarters mess, in a typical Picardy farmhouse. Recent strain between the commanding officer and some of the others led to an embarrassing pause when the senior company commander was called on to propose a toast to the C.O. On a sudden inspiration, he raised his glass and gave the toast with the words: 'Gentlemen, when the barrage lifts'."
The battalion attacked with some 800 men. Twenty-four hours later its strength was 80 men and four officers.