Rules of Engagement (novel)

Summary
From the back cover: Sudden revolution on the planet Dekkanar brings Captain Kirk and the Enterprise running to evacuate Federation personnel trapped there. But their orders from Starfleet are quite clear: the Enterprise is to assist in the evacuation, no more. No weapons are to be displayed, no shields raised, no shots fired.

Meanwhile, halfway across the galaxy, an experimental Klingon warship sets forth on a mission of its own, a warship with hidden - and therefore undreamed of - capabilities, commanded by a warrior who will stop at nothing to bring glory to the Empire - and restore his own lost honor.

The Klingon ship's destination? The planet Dekkanar...