That would be the Kriegsmarine Glücksrad.
It was a circular device segmented into 8 sections with a rotating arrow affixed to the center.
The commander would spin the arrow with one good fling and it would point to a section when the arrow stopped whirling. Whatever option the arrow pointed at would determine the course of a pending attack situation.
the options which the arrow might stop on were:
1. Attack with the Deck Gun
2. Attack with torpedo while submerged
3. Attack with torpedo while surfaced
4. Let the ship pass by
5. Crash dive, go deep, go silent
6. Call the Luftwaffe
7. Be More Aggressive
8. Please ask again later
It was a very frustrating device to use as the arrow would often stop spinning between the options, forcing the commander to try again.
this cost valuable seconds in an attack situation.
Occasionally the option pointed to by the arrow once it stopped spinning wouldnt even apply to the given situation.
In February 1940, KaptLt. Johann Bernard, in command of U-101 had to spin the little arrow no less than 7 times before the arrow pointed to something vaguely appropriate to his situation.
strangely for the first 3 spins, it landed on "be more agressive", the 4th spin resulted in the arrow coming to rest upon the "Please ask again later" option.
After waiting approximately 7 agonizing minutes so that it would be "later", kaptLt. Bernard attempted to use the device a 5th time, this time it landed on "Call the Luftwaffe" however he was several hundred miles outside of any aircraft range.
On his 6th attempt the device frustratingly said "Please ask again later" once more.
The enfuriated commander dashed the Glücksrad upon the command room floor. this lodged the arrow on "Crash dive, go deep, go silent" therfore it was the only thing he was able to do for the remainder of the patrol.
as a result of the U-101 Glücksrad Incident, BdU collected up all of the Glücksrad devices and they were destroyed; commanders were told to take whatever actions they felt the situation demanded.
unfortunately not a single authentic example of the Glücksrad exists today
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