More than 15 years ago, when the Nord Stream gas pipeline between Russia and Germany was little more than an idea, a Swedish government study warned of the risks inherent in running a critical piece of energy infrastructure along the Baltic Sea floor.
The pipeline would be vulnerable to even the most rudimentary form of sabotage, analysts wrote, and underwater surveillance would be nearly impossible. The 2007 study, written by the Swedish Defense Research Agency, even posited a scenario:
“One diver would be enough to set an explosive device.”
Today, European investigators face almost exactly that scenario. The Swedish authorities leading a criminal investigation have concluded that a state actor was most likely responsible for a September blast that ripped through the gas pipes. Officials and experts say that explosives were probably dropped from ships or — just as the Swedish report warned — planted on the seafloor using submarines or divers.
The Nord Stream attack has been a wartime mystery, prompting finger-pointing and speculation about how — in an era of constant satellite surveillance, in the midst of an energy crisis and with Europe on alert because of the war in Ukraine — a vessel could creep up on a crucial energy conduit, plant a bomb and leave without a trace.
The Baltic Sea, it turns out, was a nearly ideal crime scene. Its floor is latticed with telecommunication cables and pipes that, as had been warned, are not closely monitored. Ships come and go constantly from the nine countries bordering the sea, and vessels can easily hide by turning off their tracking transponders.
“The key question is not what kind of surveillance there was, but why the lack of surveillance for this pipeline — and other pipelines and electric cables and the underwater cables on the seabed,” said Niklas Rossbach, deputy research director at the Swedish Defense Research Agency.
The Baltic is also a giant graveyard for unexploded munitions and chemical weapons dumped after the World Wars. Expeditions to clear those obstacles are common, meaning the expertise to carry out underwater detonation is ubiquitous. Several countries along the Baltic, including Russia, have dive teams that specialize in seabed operations, officials in the region said. Russia, with a port along the Baltic, has small, quiet submarines that can move undetected, according to former military and intelligence officials in the region.