[WilhelmSchulz.]

Originally Posted by Steeltrap

the lack of the 'night' scope was largely due to the fact that the designers felt that the larger 'head' of the scope (needed to allow a capture of more light vs. day scope) made the scope too visible.....pre-war USA sub doctrines bred a real phobia about having your scope spotted into the skippers.

Interesting stuff.

http://http://www.fleetsubmarine.com/periscope.html

In order for a submerged submarine to sink an enemy ship, some means of aiming the torpedoes was required. Different navies evolved different methodologies. During the inter-war period, U.S. doctrine favored the use of Sonar for determining target range, bearing, and angle. It was believed that advances in detection and anti-submarine weapons had made it suicidal to expose a periscope in daylight. To this end, the U.S. Navy installed highly advanced Sonar and hydrophone suites in their fleet submarines, along with Torpedo Data Computers that remained significantly more advanced than anything used in any other navy until well after the war had ended.
In fact, Sonar attacks while submerged turned out to be remarkably ineffective under actual wartime conditions. Falling into one of the more common military fallacies, the U.S. Navy developed a theory, then saw test results through the lens of that theory. Any results that seemed to back up the theory were eagerly embraced, while results that failed to back up the theory were put down to "operator error." This tendency continued well into the war, to the degree that a number of commanders were relieved for "lack of agression" when the actually problem was that the torpedoes they were firing didn't work. (The Bureau of Ordinance said that the torpedoes did work, and since they couldn't possibly be wrong about that, it had to be the commanders.)