The Chouka War taught the Circasians the hard way about the importance of fighter superiority. Though the Circasian Istale Light Fighter made for a decent interceptor, the Circasians simply could not field enough of them in a fleet to combat the mass numbers of fighters -- especially assault fighters -- that an opponent to could field in their own fleet.
The Jaga Medium Fighter was designed to be the next generation Circasian fighter in more ways than one. Both the Istale and the Ruglin were designed solely for interception duties. The Circasian War Council wanted the Jaga to instead be a multipurpose fighter equally capable of dog-fighting with enemy fighter craft as well as making attack runs on enemy capital ships.
The final version of the Jaga is slow for a medium fighter, but durable and with improved firepower. The Circasians hoped for a more agile fighter, but the Jaga's other strong points helped sell it to the military and the Jaga entered widespread service within a year of the acceptance of the prototype.
During the ak-Tai War, the Jaga proved itself in combat against the ak-Tai. The Jaga was not as fast or nimble as the ak-Tai equivalents, but the organic integration of Circasian fighter forces into the existing Circasian battle line made them very effective in their given roles.