In Great Waters 1939-45: The Epic Story of the Battle of the Atlantic 1939-45; by Spencer Dunmore.

The subject is sort of a side facet of the whole history of the war, with main stage being the continent of Europe and the second, perhaps more important, being the resolute holding on by British, and the later tough fight by Russians.

But all along, the battle of Atlantic was a key factor, and Allies could not afford to lose it or give way any more than the world could afford to make treaty and stop fighting in name of wistful dreaming of Peace, which sometimes one has to win when endangered by forces against it.

Britain could then fight openly, but however convinced Roosevelt was that the forces of darkness had to be defeated, he was bound by the various facets of his nation that he had to herd along before he could join his nation in the battle on the side of right.

The battle of Atlantic is here told in some detail, with descriptions of U-boats attacking convoys ferrying hundreds of thousands of soldiers, and in turn the British giving a tough fight back. There is the Enigma and its having been broken and yet the necessity of keeping the fact secret - and hence sacrifice of unsuspecting sailors. There is the various instances of British treating the pow Germans well, to their surprise, since they had been doing the opposite and expected the worst treatment in return.

There is the background of U-boat, the so named wolf pack that was officially and otherwise much celebrated in Germany, since they were perceived as the front and the dangers of their lives very well understood. However, they succeeded for long enough to forget about the last part and then had surprises.