The Waagoshin Invasion is the term used by the Tch'Kairn and their allies the Niglik and the Joz to define the passage of time beginning with the initial invasion of Nigli to the final liberation of the allies.
The invasion began in 2198, when the Waagoshin chose to conquer the otherwise peaceful Niglik when they felt that the niglik were not sharing their more advanced technology with the Waagoshin at a rate that they preferred.
Although more technologically advanced, the Niglik were fairly peaceful and completely unprepared for the sheer brutality of the Waagoshin invasion. Within 10 years, the planet had fallen to the Waagoshin and the assault force moved on to invade Tch'Kair, who had shared technology with the Niglik during the war.
In 2208, the waagoshin invasion fleet reached the Sigma Draconis System and homeworld of the Tch'Kairn. As the tch'kairn were truly pacifists they gave no resistance through conflict and were easily subdued.
After a hundred years of occupation, the Tch'Kairn Resistance formed to liberate their planet from Waagoshin rule. Their leader K'Thartek managed to send out a signal requesting aid which was answered by the United Federation of Planets. True to their nature, the Waagoshin attacked the Federation starship USS Hades and as a result declared a de facto war against the UFP.
The crew of the Hades allied with the Tch'Kairn and Niglik members of the resistance and through military action managed to decimate the Waagoshin military forces. Tch'kairn was the first planet to be liberated.