The tunnel opened on February 2, 1862, on the rail line connecting Paris to Laon through the Aisne countryside about forty kilometers south of Laon. From the start, the ground fought back. The soil was composed of weak granite that made construction treacherous. When the French Army blew up a section during the retreat of 1914, the blast left a cavity above the structure. Rather than filling it, engineers in 1915 decided to incorporate the void into the vault by reinforcing it with masonry. The resulting repair was visibly different from the original: the ceiling at that point was noticeably higher, a scar the tunnel wore for decades. By 1972, little had changed. The section beyond Crepy-en-Valois still ran diesel trains on two tracks, allowing trains traveling in opposite directions to pass each other inside the tunnel. Early that year, SNCF engineers noticed cracks in the vault and falling bricks. They began a renovation, removing damaged masonry, installing temporary supports, and spraying shotcrete. The demolition, however, moved faster than the repair work that was supposed to follow it.

At 8:21 PM on June 16, a deadheading locomotive crossed through the tunnel without incident. It was the last train to pass safely. Shortly afterward, seven hundred cubic meters of rock and debris crashed down as the vault partially collapsed, blocking both tracks. At 8:54 PM, Train 2841 from Paris to Laon entered the tunnel at 108 kilometers per hour. The train was unusually full: students and workers heading home for the weekend, soldiers on leave. The lead car slammed into the debris and stopped violently. The second car was flung sideways by centrifugal force, tearing free and coming to rest parallel to the first at the foot of the landslide. The third car piled into the wreckage. Two minutes later, at 8:56 PM, Train 7844 bound for Paris entered from the opposite end. Its lead car rode up the slope of fallen rock and embedded itself in what remained of the tunnel vault. The second car crushed the rear of the first.

The conductor of Train 7844 reached a trackside telephone at 9:11 PM and called Vierzy station. Eight volunteers arrived before the general alarm was raised. By 10 PM, the Aisne department activated its emergency ORSEC plan. At the height of the operation, five hundred rescuers worked inside the tunnel in total darkness and suffocating heat, navigating through tangled sheets of metal to reach the trapped. The work continued for days. On Monday, June 19, officials declared there was no further chance of finding survivors. The last debris was cleared by June 23. One hundred and eight people had died, making it the deadliest rail accident in France since the Lagny-Pomponne disaster of 1933 and the third deadliest in French rail history.

The investigation commission determined that the collapse stemmed from the repair work itself. The demolition of damaged brickwork had outpaced the subsequent reinforcement phases, leaving a long stretch of vault exposed and unsupported. The tunnel's century of accumulated damage, from poor original materials to wartime explosions, had left it fatally fragile. The Rerolle Commission published its findings in the Official Journal on April 11, 1973. When Minister of Transport Yves Guena addressed the National Assembly, the conclusion was plain: the sequence of construction phases, where demolition proceeded faster than the steps that should have followed, was the ultimate cause. The tunnel was rebuilt with new lining, its width reduced to a single track. A memorial stele now stands above the Paris entrance, bearing a quote from the author Romain Rolland: "Fate is the excuse of souls without will." At the Abbey of Saint-Leger in Soissons, where all 108 bodies were gathered, another monument carries their names.