By April 1945, Kranzbühler was brutally beaten, arrested, detained and interrogated for approximately four weeks by Allied Forces, along with other German navy judges.

As a result, he wanted to make it immediately clear to the tribunal that, though on the losing side of the war, Dönitz's actions were not deserving of the indictments brought against him.

Kranzbühler argued that if the Grand Admiral of the German Navy was to be tried, he should be addressed by the court with the respect he deserved as a military leader.

The U-boat Arm was the principal part of the German fleet – with its submarines sinking millions of tons of allied and neutral shipping.

To defend Dönitz against the charge that orders to sink merchant vessels were illegal, Kranzbühler brilliantly presented to Fleet Admiral Chester W. Nimitz, commander of the United States Pacific Fleet, an interrogatory in which he extracted various items of information about American naval practice.

Yet, unlike in the merchant ship argument, Kranzbühler was unable to attain an affidavit from Allied Forces that Americans had done the same – even though they arguably did.

As a result, by issuing these two orders Dönitz was found guilty of causing Germany to be in breach of the Second London Naval Treaty of 1936.

Once again, Dönitz's order to conduct unrestricted submarine warfare was not officially included in his sentence; however this was still the main reason why most judges wanted him convicted.

Dönitz served 10 years in Spandau Prison plus the additional 5 months he had spent at Mondorf and Nuremberg while awaiting trial and being tried.

According to Kranzbühler years later "As I learned later on, an American law advisor made the proposal to the Allied control office to nullify the verdict."

Kranzbühler believed that the prosecutors and judges made it very difficult for the defense to efficiently represent the defendants at Nuremberg.

Furthermore, the defense was only allowed to use German material, meaning that all foreign archives remained strictly barred from review or submission.

Instead, the defense had to prove its existence through numerous affidavits that were subject to continued objections on the part of the Russian prosecutors.

Although, in this instance, the defense reached its ultimate intent, they had to spend time calculating ways in which such foreign evidence could be introduced.

When the defense demanded that these documents be made available to them in the German original before being submitted to the court, the prosecutors and judges refused.

According to Kranzbühler, in an in camera meeting regarding this issue, Chief Prosecutor Robert Jackson refused to submit the original documents because it would be contrary to the purpose of the Nuremberg Trials.

To the surprise of Kranzbühler, Jackson argued that the purpose of the trials was not to bring criminals to conviction, but rather to (1) prove to the world that the German conduct of war had been illegal and unjustified just as the U.S. had alleged throughout the world by her propaganda before her entry into the war; and to (2) make it clear to the German people that it deserved severe punishment, and to prepare them for such punishment.

Kranzbühler believed it to be an injustice that the laws at Nuremberg were constructed not around what is legally correct, but what would be sufficient to convict those they wanted to punish.

Rather, in defining the legitimacy of the indictments, Kranzbühler found it more useful to evaluate the laws and their likelihood of being reapplied by future courts, regardless of whether they were present prior to Nuremberg.

Kranzbühler doubted that the legal concept of a war of aggression could be applied in the future when the term is so difficult to define.

Kranzbühler concluded that the finding of a war of aggression is a political problem – that a court is unlikely to declare the victor 3.

In this regard, Kranzbühler concluded that the International Military Tribunal proceedings discharged the tensions between the victors and the vanquished.

He served for many years on the board of directors for Rheinmetall, a German automotive components and defense equipment company.