The Master and the Messenger by Kenneth McKay

The Master and the Messenger is a story of an American army general and his act of betrayal in the depths of a Bavarian winter. A series of disturbing events set the action in motion in the first three-month period of 1983.
On the first day of the new year General Gregory Keech defects from his base in West Germany. The US is outraged and accuse the Soviets of his abduction. With UK assistance, a plan is drawn up to locate and deliver their general back to the States and to the waiting media. Unknown to the US services a high level mole is discovered within British Intelligence.
The story unfolds in London, Paris and Bayreuth. A race is on to help the American rescue their general in London while they dig deep to root out their mole.