Soviet engineers began construction in 1958 as part of a broad infrastructure program across Afghanistan -- roads, bridges, and tunnels that would bind the country together and, not incidentally, bind it closer to Moscow. The tunnel was completed in 1964, running 2.67 kilometers beneath the Salang Pass and emerging on both sides into a landscape of switchback roads and avalanche galleries. Before the tunnel existed, the primary route between Kabul and the north ran over the Shibar Pass, a journey of roughly three days. The tunnel compressed that to hours. When the Soviet Union invaded in December 1979, the infrastructure it had built became its own supply line. Military convoys rolled through the Salang Tunnel day and night, carrying fuel, ammunition, and troops to sustain an occupation that would last a decade. The gift had become a weapon -- wielded, eventually, by both sides.

The tunnel's dimensions tell its story. Some sources describe it as seven meters wide and seven meters high; others say no more than twenty feet at the base and sixteen feet at the center. Either way, it is cramped, dark, and choked with exhaust fumes from the vehicles that pack it far beyond capacity. Ventilation has always been inadequate. On February 23, 1980, a road collision trapped a Soviet convoy inside, and 16 soldiers suffocated from carbon monoxide poisoning before anyone could reach them. Two years later, on November 3, 1982, a far worse catastrophe struck: a collision involving a fuel tanker ignited a fire that engulfed a military convoy. Soviet records acknowledge 64 soldiers and 112 Afghans killed. Western sources estimate the death toll at 2,700 to 3,000 -- a number that, if accurate, would make it the deadliest road incident in history. Neither the Soviet nor Afghan governments ever officially confirmed the fire occurred.

In 1997, Ahmad Shah Massoud's forces destroyed the tunnel to halt the Taliban's advance northward. For five years, the Hindu Kush was once again impassable by road in winter. In 2002, the Russian Ministry of Emergency Situations sent crews who rebuilt the tunnel in a single month. Traffic resumed -- and immediately exceeded what the infrastructure could bear. By the early 2010s, ISAF was funding repairs and renovation, and USAID commissioned a technical study for an entirely new tunnel that would run from Olang in Parwan Province to DoShakh in Baghlan Province, bypassing the aging bore entirely. That replacement has yet to be built. In 2023, major construction work was undertaken inside and outside the existing tunnel, a structure now nearly sixty years old and showing every one of those years in its cracked walls and failing ventilation.

Avalanches are as much a threat as the tunnel itself. In January 2009, slides on the approach roads killed at least ten people. In February 2010, a series of avalanches struck in rapid succession, burying miles of highway, killing at least 166 people, and trapping hundreds of vehicles -- some inside the tunnel, some beneath meters of snow on the open road. The Afghan National Army and NATO helicopters rescued approximately 2,500 stranded travelers over four days before the road reopened on February 12. Then on December 18, 2022, a fuel tanker exploded inside the tunnel, killing at least 31 people and injuring 37 others -- a grim echo of 1982. Each disaster prompts talk of modernization, of a new tunnel, of better ventilation and traffic controls. And each time, the old tunnel reopens, and the vehicles squeeze back through, because there is no alternative. The Hindu Kush has one door, and this is it.