Wasp - Eric Frank Russell

The war had been going on for nearly a year and the Sirian Empire had a huge advantage in personnel and equipment. Earth needed an edge. Which was where James Mowry came in.
If a small insect buzzing around in a car could so distract the driver as to cause that vehicle to crash, think what havoc one properly trained operative could wreak on an unsuspecting enemy.
Intensively trained, his appearance surgically altered, James Mowry is landed on Jaimec, the ninety-fourth planet of the Sirian Empire. His mission is simple: sap morale, cause mayhem, tie up resources, wage a one-man war on a planet of eighty million. In short, be a wasp.
First published in 1957, Wasp is generally regarded as Eric Frank Russell's best novel , a witty and exciting account of a covert war in the heart of enemy territory.