Subspace inertial displacement was a characteristic of subspace particles. In 2368, a cloaked fleet of Romulan Warbirds fired tachyons into the tachyon detection grid of Starfleet to sabotage and pass the blockade. The result was a subspace inertial displacement which could be detected by Federation starships like the USS Sutherland under the command of Lieutenant Commander Data. (TNG: "Redemption II" )