In 2371, a Cardassian informant told Odo that a number of Romulan ships, believed to be warbirds, were detected near the border, along with troop movements and increased communications activity. The informant admitted the Cardassian authorities considered this a possible prelude to a Romulan invasion, but that this made little sense. Central Command was unaware that the buildup was actually part of a top secret, joint Obsidian Order-Tal Shiar operation to launch a preemptive first-strike against the Founders' homeworld. (DS9: "Improbable Cause")