A Game for Heroes — Jack Higgins

The days of the Third Reich are numbered … but on an isolated island outpost in the middle of the English Channel, the German army has vowed to fight to the death. Under a brilliant, ruthless S.S. commander, the Nazi invades have turned the once-peaceful island into an impregnable fortress.
The mission of Owen Morgan, British soldier of fortune, is to lead a ruffian band of hardened commandos onto the island in bold move that could destroy the enemy one and for all … and destroy themselves as well…