ROSTOCK, Germany—The small marina on the edge of this north German city is a popular summertime spot for recreational sailors. German intelligence believes it was also the jumping-off point for the sabotage of the Nord Stream gas pipelines, an assault on Europe’s civilian energy infrastructure unprecedented since World War II.
On Sept. 6, a small group set out from Rostock aboard a rented yacht, the Andromeda, a slender 50-foot-long, single-masted sloop, ostensibly on a pleasure cruise around Baltic Sea ports. Within two weeks, the group returned the boat and disappeared.
