Dust on the sea - Douglas Reeman

It is 1943, and Captain Mike Blackwood, Royal Marine Commando, is a survivor. Young, toughened and tried in the hellish crucible of Burma, he labours, sometimes faltering, beneath the weight of tradition, the glorious heritage of his family, and the burden of his own self-doubt.
For Blackwood, the horizon is not the lip of the trench seen by men of the Corps in the previous war, but the ramp of a landing craft smashing down into the sea, and the fire of the enemy on a Sicilian beach. Here, tradition is not enough, and Mike Blackwood must find within himself qualities of leadership which will inspire those Royal Marines who are once again the first to land, and among the first to die.
This is the fourth novel in the Blackwood saga, spanning 150 years in the history of a great seafaring family and the tradition in which they served.