The Great War was the period of time, about 1000 years, which occured after the Great Rescue. It started when Teridax teleported Vakama with the Vahi on Mata Nui and the other Toa Metru, along with him, sacrificed their Toa Power to awaken the Matoran. They had 1 year to prepare for a new assault from Teridax. Things also happened in different lands during this period.