The coming of war usually leads to demands for more personnel, and more officers to command them.  In Which They Served examines the routes to commissions in the Royal Navy during World War II and the ways in which war-time only officers served, most often on escort duty in the Battle of the Atlantic or commanding smaller vessels such as landing craft.  This is done quite well, though naturally Lavery, Curator Emeritus of Britain's NationalMaritimeMuseum, Greenwich, necessarily passes over regular pre-war officers, and the "Big Ship" navy. 

In telling the story, Lavery draws upon the memoirs, experiences, and writings of a good many officers, among them the novelist Nicholas Monsarrat, who spent much of the war on convoy duty, and based his brilliant The Cruel Sea on personal experience, the actor Alec Guinness, who commanded a landing craft and for a time ran supplies to Tito's Partisans, and even the author Evelyn Waugh, who served in the Royal Marines, as well as many otherwise quite obscure men. 

The book takes the officers-aspirant from recruitment through training, and on into the war, in the process proving much information about life in the Royal Navy and the ways in which it fought, including escorting convoys, beaching landing craft and sinkings. Invaluable for those interested in the Royal Navy or war at sea.