The Radical Factor - Stone Blade, #3

The Semids are a peaceful people and staunch friends and trade partners of the League since the formation of their Federation of Worlds. When a group of interstellar terrorists detonates a nuclear bomb at the dedication of their Peace Spire the Semids call on the League for help tracking them down. Micah Stone and his team embark on a journey of action, intrigue and interstellar trade to track down the ones responsible and bring them to justice.
The strangeness of the cultures and the planets they encounter is almost as bad as the foes they seek and they must learn to adapt quickly or face death through sheer ignorance. At the end of their journey the League agents find a 'civilization' of interstellar barbarians willing to wage war at the drop of a hat. Then, to their disgust, they discover that the barbarians are operating at the orders of the real enemy and that enemy is almost impossible to defeat!