The Praetor Campaign was a Romulan preemptive strike into the Gamma Hydra Sector which had taken place in the past of a simulation created for William T. Riker.
In 2367, while exploring a cavern on Alpha Onias III, Commander Riker was rendered unconscious by gases. While unconscious, neural scanners scanned Riker's brain. The scanners used elements of Riker's reality and constructed a simulation with those elements interspersed throughout, so that it felt real to him. What Riker wanted, the scanners made possible.
During this incident, swift intervention of the USS Titan, under the command of Captain Riker, prevented the strike from occurring. In 2383 of this simulation, this campaign was mentioned in Riker's service record that was on display in his quarters on the Enterprise-D. (TNG: "Future Imperfect", okudagram)