From Wookieepedia, the Star Wars wiki.
The Duinuogwuin Contention took place in 15,500 BBY (in the Indecta Era) when Coruscant was assaulted by Duinuogwuin.
The conflict was sparked by a disastrous first contact when Republic scouts reacted fearfully when they encountered these fifty-meter long serpentine beings that soared through space breathing atomic fire. The Star Dragons then pursued the scouting fleet back to Coruscant and waged war on the Republic.
The conflict was ended in peace by Supreme Chancellor Fillorean and the Star Dragon philosopher Borz'Mat'oh, who together founded the University of Coruscant.