Why did germany use "prize regulations"?

[BigWalleye]

Clay Blair is hardly a Nazi apologist, but his version is different and far more nuanced than the brief summary you present.

The evolution of the standing orders was gradual and based on many factors.

And some of the statements you do not quote are suppositional, such as:

Originally Posted by Von Tonner

He however, quickly changed his views and agitated for a "unrestricted war" by his U-Boats.

Early in the war, Donitz made the false assumption that a good many of his boats that failed to return were destroyed while abiding by Prize Regulations.

... if the Prize Regulations were enforced Britain would simply place its merchant fleet under a neutral flag.

Your last quote bears not so much on the Prize Regulations, which dictated that crews of seized ships were to be adequately provided for before the ship was sunk, but on the treatment of survivors of sunk ships. As such, it post-dates the abandonment of the Prize Regulations, at least by the on-scene U-boat commander. An attack carried out in strict accordance with the Prize Regulations would leave no one in need of rescue.

"Rescue no one and take no one with you. Have no care for the ship's boats. Weather conditions and the proximity of land are of no account. Care only for your own boat and strive to achieve the next success as soon as possible! We must be hard in this war. The enemy started the war in order to destroy us, therefore nothing else matters"

This quote was in response to numerous incidents, including at least one attack on a U-boat crew which was trying to assist survivors - by the survivors themselves.

Peter Padfield's War Beneath the Sea, written by an unabashed Anglophile and ardent admirer of the Royal Navy, makes an interesting read, but IMO his portrayals need to be viewed in the context of other, more objective works. Padfield claims an uncanny ability to know what was in Doenitz's mind, even in the absence of documented evidence, and occasionally "quotes" from conversations for which no record exists. YMMV

You fail to mention the ambiguous situation created by "neutral" merchants which began transmitting "SSS" on sighting a surfaced U-boat, thus making themselves part of the Allied ASW apotting force in accordance with "international law".

As I said in my first post, the whole story of the German observance and later abandonment of the Prize Regulations is complex, and even relatively lengthy posts in an online forum can not do it justice.

Of course, the United States, after the Pearl Harbor attack, considered that Japan had abrogated all international conventions on the conduct of warfare and felt free to wage unrestricted submarine warfare from the start.