Caleb IV was the fourth planet of the Caleb system, and it was the site of a Federation outpost in the 23rd century.
Although it has not been clearly stated on screen, it was likely Caleb IV was located near the Federation-Klingon border.
In the 2260s, it was attacked by two Klingon divisions led by Kang and Kor. Aboard the D5 class cruiser IKS Klothos, Kor outmaneuvered the defending Federation forces by attacking with an initial feint, and then returning with his full force, catching the Federation in the midst of their repair work.
A century later, during a similar attack on a Dominion base at Trelka V, Kor believed that he was back at Caleb IV. (DS9: "Once More Unto the Breach")
According to the Star Trek: Star Charts, on page 57, the Caleb system was also known as Kaleb and Chi Eridani. This was a binary star system. Both the primary and secondary stars were G-type stars. Caleb IV was located in the Beta Quadrant. On page 66, the Kaleb sector derived its name from the Caleb system.