The Karsid Empire invaded Klinzai in 1425. Reaction to the invasion was strong, but the Karsids were quite superior technologically. Klingon groups used terrorist tactics, but were unable to topple the Karsid regime for many centuries. It was finally the first incarnation of the Klin Underground that was able to assassinate many of the Karsid leaders and organize the people into an effective defense against retaliation. After the threat of counter-revolution was over, Klingon leaders assuaged the crippled pride of the people by destroying all records and traces of the Karsid occupation. Today, the only records that exist of this time period are those from the Karsid Empire itself. Those records were discovered by the Federation when occupying Starbase 12. Two historians, Trae of Vulcan and Khlaru of Klinzai have been working for five years on cataloging the records and expect to publish their findings within the next five years.