Arctic convoys continued - - intelligence!
"When the chances on both sides are equal, it is
Intelligence that makes one able to look down on
one’s opponent, and which proceeds not by hoping
for the best (a method only valuable in desperate
situations) but by estimating what the facts are,
and thus obtaining a clearer vision of what to
expect." - - Pericles to the Athenians.
The British Royal Navy having access to Ultra intelligence throughout the war and able determine with regularity and accuracy the dispositions of the German naval detachments in Norway, threatening the Arctic convoys, communications intelligence of tremendous value when evaluating the threat as posed to the convoys by the German "gauntlet"!
AND also having access to in an informal manner to the high level message traffic of the German naval most senior command LAND LINE COMMUNICATIONS secured by a cryptographic machine of a higher level of security than Enigma!
German secure land line communications with those naval forces in Norway subject to intercept [wire tapping] by Swedish authorities, the "secure" teleprinter messages of importance "read" - - noteworthy intelligence gleaned and passed to the British as determined by word of mouth and informally!!
These supposedly secure land line encrypted message traffic "read" thanks to the amazing efforts of the famous Swedish cryptanalyst Arne Beurling!!
[Beurling accomplished what he did in two weeks, not having other than message traffic to deal with, NOT having a vast array of analytical machines, a team of analysts, or even having a "peek" at the machine itself!]
The German Geheimfernschreiber secret and supposedly secure on-line cryptographic machine not so secure. The Geheimfernschreiber called Sturgeon by the British!
As to Arne Beurling and his achievement, monumental in nature, we have this excerpt from the wiki:
"In the summer of 1940 he [Beurling] single-handedly deciphered and reverse-engineered an early version of the Siemens and Halske T52 also known as the Geheimfernschreiber (secret teletypewriter) used by Nazi Germany in World War II for sending ciphered messages. The T52 was one of the so-called 'Fish cyphers' and it took Beurling two weeks to solve the problem using paper and pen. Using Beurling's work, a device was created that enabled Sweden to decipher German teleprinter traffic passing through Sweden from Norway on a cable."
"While the Enigma machine was generally used by field units, the T52 was an online machine used by Luftwaffe and German Navy units, which could support the heavy machine, teletypewriter and attendant fixed circuits. It fulfilled a similar role to the Lorenz SZ40 and SZ42 machines in the German Army."
And for the Swedes to violate their neutrality as they did during the war even if informally to the advantage of the allies it was all altruistic and a big thank you is in order? Or the Swedes had more practical reasons for doing what they did? I cannot say for sure.