How Old?
 

Does anyone know how old a LT Junior would be? One that is captain of a U-Boat?

Depends on the year of the war. U-Boat.net has a listing of all the Kaleuns and their birthdays. I suspect you will find they probably were close to 30 when the was started and probably much younger in 1945.

Early in the war, the minimum age to command a U-boat was 25. The oldest commander was the commander of the Milk Cow U-459 who was (IIRC) 47!

As the war ground on, the age requirement went down and the youngest Kaleuns ever (again IIRC) were 19 and 20.

Correct :yep:

There were also guidelines for promotions, which in wartime were at least 1.5 years of service before moving up from Oberleutnant to Kapitanleautnant, or from Kapitanleutnant to Korvettenkapitan.

There were many very successful young commanders though. My favorite Mohr, was a highly-decorated Fregattenkapitan by 1943, and he didn't even live until his 27th birthday (and he was one of those who was only allowed command when he reached 25)...

Information extracted fro U-Boat net:

Who was the youngest commander?

The youngest commander was Leutnant zur See Ludwig-Ferdinand von Friedeburg . He took over the command of U-155 on 15 August 1944. He was then 20 years and 3 months old. There were 3 others Leutnants who took over a boat while only 20 years old: Hans-Eckart Augustin (U-62), Gerhard Ady (U-704) and Hans-Joachim Dierks (U-14). They were all training U-boats.
The youngest combat U-boat commander is often considered to be Oberleutnant zur See Hans-Georg Hess of 21 years. He won later with his U-995 the Knights Cross. But von Friedeburg was still younger and certainly qualifies.
During the first years of the war there was a strict rule, that a commander had to be at least 25 years old. So "Teddy" Suhren, then already a Knights Cross owner, had to wait for a few months in a training unit until he was old enough.

Who was the oldest commander?

The oldest Commander was Fregattenkapitän Wilhelm Kiesewetter . He took over the command of UC 1 on 20 November, 1940. He was at that time 62 years old! That was a former Norwegian boat and only used in training units. In WWI Wilhelm Kiesewetter was Commander of SM UC-56.

The oldest Commander on patrol during WWII was Korvettenkapitän Georg von Willamowitz-Moellendorf, the well known commander of U-459, one of the Milk-Cows. He died in 1943 at the age of 49 years.
The usual limit for combat-commanders was 40 years.

Interesting info..:know: