The Lochnagar mine.
With over three million men fighting in it and over a million dead or wounded, the Battle of the Somme, raging from July 1 to November 18, 1916, is one of the bloodiest battles in history and one of the defining operations of the First World War. Today we are going to look at how the battle was kicked off by the largest explosion and the loudest sound created by man up to that point.
The lines of the Somme front were stabilized by the end of 1914. By Christmas Day the French were already digging tunnels towards the German lines close to the ruined village of La Boisselle, lying on the extreme edge of German-held territory. For the next year and a half, the ground around the village was crisscrossed by French-British and German mine galleries trying to undermine the enemy’s trenches or trying to intercept and cave in the other side’s tunnels.
The Battle of the Somme proper started as a massive Entente offensive against the Germans on July 1, 1916. In preparation of the attack, British tunneling companies prepared 19 mines under German lines. La Boisselle lay right along the axis of the British advance and four mines were prepared here: two medium-sized ones with 8,000 lbs of explosives each, the Y Sap to the northwest of the village with 40,000 lbs of explosives and Lochnagar to the southeast with 60,000 lbs. The latter two were named after the section of the trenches where the digging began.
The idea was that besides killing and surprising the Germans, the two smaller explosions would throw enough dirt around to create barriers against gunfire, while the two large craters, once occupied, could be used to spring an attack both on the village from two sides and at the second line of German defenses to the east. To protect the troops that would go into the crater, the mines were “overcharged” by placing enough explosives that the resulting blast would give the craters extraordinarily wide and tall lips for a natural barrier.
Work had to be done extremely quietly to avoid being detected by German listening posts. The tunnel floors were covered in sand bags and tunnelers moved about barefoot. Running through a chalky layer of the ground, the tunnels were excavated with bayonets and every single piece of flint that was dislodged had to be removed by hand without it hitting the floor and making a noise. When someone dug with both hands, another man had to stand next to him to catch any loose bits. The Lochnagar tunnel was only 2.5 by 4.5 ft wide, but the extreme caution still slowed progress to 18 inches per day on average.
The main tunnel ran about 50 ft underground and crossed a distance of about 900 ft, terminating close to the German lines. Near the end, the tunnel branched and terminated in two chambers, which were filled up with a total of 60,000 lbs of explosives. The chambers weren’t large enough to house it all, so the split tunnels were also filled up and the area was sealed off with some of the chalk that was removed during the digging.
During work, the tunnelers became aware of German sappers working above the Y Sap and below the Lochnagar mines, trying to locate British tunnels. Later, the British found the German tunnels and learned that the one near the Lochnagar mine was a mere five feet away from breaking through and finding them. Before the attack, additional tunnels were dug in the vicinity of the site. Once the mines were blown, these would be quickly finished so troops could emerge directly inside the crater.
The first mines were detonated at 7:20 a.m. on July 1, Lochnagar and Y Sap following 8 minutes later. According to some reports, the detonation of the Lochnagar mine, the largest artificial explosion in history up to that point, could be heard in London. A patrol plane flying some two miles away was flung sideways by the pressure. The Lochnagar explosion obliterated German dug-outs, likely full of soldiers, along a 300-400 ft stretch of the front. The crater was 220 ft across without the lip.
For all that destruction, the mines ultimately proved to be a failure. The Y Sap mine was detected in time and German soldiers were evacuated and incoming British troops were caught in a crossfire. The Lochnagar crater was quickly occupied by British forces who then proceeded eastward to the German second line but were then pushed back into the crater. Friendly fire from British artillery started killing the soldiers inside, only stopping when an airplane noticed the incident. The 34th Division of III Corps, charged with securing the two craters, suffered the highest casualties among all units on that day. Symbolic of the pointless struggle of trench warfare, the village of La Boisselle was supposed to be captured in 20 minutes but was only secured on July 4, 1916 after changing hands several times.
The Lochnagar crater was bought by an Englishman after the war and can still be visited today; the Y Sap crater was filled in. You can visit the spot and learn more about the role engineering played in the Great War on our Fields of World War 100 I Tour and visit the Western Front on the 100th anniversary of the end of the war to end all wars.