Treaty of Sirius
The Treaty of Sirius was the peace agreement between Earth and the Kzinti, signed in 2069. After a humiliating defeat in the Earth-Kzin Wars, the Kzinti had little choice but except the provisions of the treaty. These included a demilitarization of the government, a reduction of their fleet to a few police vessels, and unrestricted access to Kzinti space. (The Animated Series: "The Slaver Weapon")
The Kzinti would harbor ill feelings for centuries against Earth and the Federation.