The Battle of Britain Five Months That Changed History, May—October 1940 by James Holland (z-lib.org).epub

continually refined his estimates, so the different information would be
programmed into a kind of calculator, which would then produce the DA.
As soon as the Captain was happy, he would give the order to fire.
All this needed to happen very quickly, and there is no doubt that the
best way to assess range, course and speed was through snap assessments
made by the naked eye. And this was where experience, allied to a calm,
calculating mind and a dash of decisiveness made all the difference.
Making these calculations and decisions at two minutes to eight o’clock
on the morning of 2 July was Kapitänleutnant Günther Prien of U-47. Still
off the south-west coast of Ireland, U-47 had, for the past twenty-four
minutes, been tracking a large liner. The U-boat had just one torpedo left –
one that had been defective but, Günther hoped, had been successfully
repaired by Peter Thewes, the Ober-Mechanikersgefreiter, the
Torpedoman’s Mate. Now peering through the attack periscope, Günther
had already made a difficult decision. The ship filling the glass was a liner,
and at first he had wondered whether it might be neutral, such as an
American passenger liner. But then it had started to weave, which suggested
it was British or steaming in British interests. Now, as it turned again,
Günther gave the order to fire.
Günther Prien had been born with the sea in his lungs, at the Baltic port
of Lübeck, one of three children and the son of a judge. His parents
divorced when he was young, however, and they moved to Leipzig, but in
the post-war economic crisis his mother fell on hard times, so in 1923, aged
just fifteen, Günther left home and joined the merchant marine, having
spent his last few marks on a three-month course at the Seaman’s College in
Finkenwärder. Beginning his life on the sea as a cabin boy on a sailing ship,
he spent the next eight years in the merchant service, rising steadily through
the ranks and learning much about seamanship but also how to look after
himself. By the time he had his master’s certificate, however, there were
few captain’s jobs going and he found himself out of work. Life soon
picked up, however, as he learned that the expanding German navy was
offering its officer candidate programme to merchant marine officers. He
applied, was accepted, and so in January 1933, aged just twenty-five, he
joined the German navy. Two years later, having been commissioned,
married and had a baby daughter, he volunteered for the U-boat arm. There
he prospered, going on to be the third – and youngest – commander of the
new Type VII U-boats.