In July 2000, US intervention in the Penamstan Civil War goes awry when an Army helicopter is shot down. An Army special operations unit, the "Mad Dogs", are sent to the crash site as a rescue mission, but find they have become Zombies. The incident is classified, and the soldiers are returned to Texas as heroes for their fighting against the guerrillas. Six years later, evidence is discovered by TerraSave activist Claire Redfield, which reveals an expansive conspiracy to cover-up the deployment of bioweapons. Meanwhile, the White House is placed on alert after a mole steals top secret files regarding the Shanghai Institutes for Biological Sciences, followed soon-after by the use of bioweapons there. In the aftermath of the incident, now covered-up too, Army operator Leon S. Kennedy meets with Redfield and discovers the incidents in 2000 and now are linked. Source: Resident Evil Wiki