Why did Shirer omit information from The Rise & Fall of the Third Reich?

Question

In The Rise and Fall of the Third Reich in the section on the early life of Adolf Hitler, William Shirer brings some memos from the teachers of Adolf Hitler as a recollection from the time he was their student at Linz.

William Shirer wrote that the history professor Dr. Leopold Poetsch was the only professor Hitler liked and that was mentioned in his book Mein Kampf.

It was perhaps decisive for my whole later life that good fortune gave me a history teacher who understood, as few others did, this principle …—of retaining the essential and forgetting the nonessential … In my teacher. Dr. Leopold Poetsch of the high school in Linz, this requirement was fulfilled in a truly ideal manner. An old gentleman, kind but at the same time firm, he was able not only to hold our attention by his dazzling eloquence but to carry us away with him. Even today I haired man who, by the fire of his words, sometimes made us forget the present; who, as if by magic, transported us into times past and, out of the millennium mists of time, transformed dry historical facts into vivid reality. There we sat, often aflame with enthusiasm, sometimes even moved to tears … He used our budding national fanaticism as a means of educating us, frequently appealing to our sense of national honor. This teacher made history my favorite subject. And indeed, though he had no such intention, it was then that I became a young revolutionary.

Why did Shirer omit some info in lines 3 4 and 14. Is that how they were mentioned in Mein Kampf? Or was it unrecoverable pages from back then ?

Answer 1

Note the triple dots, called an ellipsis, standing in for the omitted text in your quote:

ellipsis
the omission from speech or writing of a word or words that are superfluous or able to be understood from contextual clues.

As noted above, this is used when the complete text contains superfluous words and phrasings that would distract from the point being made by the author. To be an honest usage, of course, the omitted words must not affect the original meaning when omitted.

Answer 2

This is the text quoted (in a different translation). If that was Shirer's punctuation, and if the translation is accurate, then Shirer's punctuation was misleading:

To 'learn' history means to seek and find the forces which are the causes leading to those effects which we subsequently perceive as historical events.

The art of reading as of learning is this: to retain the essential to forget the non-essential.

Perhaps it affected my whole later life that good fortune sent me a history teacher who was one of the few to observe this principle in teaching and examining. Dr. Leopold Pötsch, my professor at the Realschule in Linz, embodied this requirement to an ideal degree. This old gentleman's manner was as kind as it was determined, his dazzling eloquence not only held us spellbound but actually carried us away. Even today I think back with gentle emotion on this gray-haired man who, by the fire of his narratives, sometimes made us forget the present; who, as if by enchantment, carried us into past times and, out of the millennial veils of mist, molded dry historical memories into living reality. On such occasions we sat there, often aflame with enthusiasm, and sometimes even moved to tears.

What made our good fortune all the greater was that this teacher knew how to illuminate the past by examples from the present, and how from the past to draw inferences for the present. As a result he had more understanding than anyone else for all the daily problems which then held us breathless. He used our budding nationalistic fanaticism as a means of educating use frequently appealing to our sense of national honor. By this alone he was able to discipline us little ruffians more easily than would have been possible by any other means.

This teacher made history my favorite subject.

And indeed, though he had no such intention, it was then that I became a little revolutionary.

The third instance of ellipsis, Shirer thought was not necessary to quote. That's debatable: relating past grievances to present day grievances is exactly how you transform a history student into a "little revolutionary". But Shirer gets to make the call about how much he wants to cite for what purpose.

But according to your citation, Shirer starts his quote with:

It was perhaps decisive for my whole later life that good fortune gave me a history teacher who understood, as few others did, this principle …—of retaining the essential and forgetting the nonessential …

This would properly have been punctuated as

It was perhaps decisive for my whole later life that good fortune gave me a history teacher who understood, as few others did, this principle [of retaining the essential and forgetting the nonessential]

—the bracketed comment is something inserted by the quoter to explain context. (In this instance, the paragraph just before where Shirer starts his quote.)

In fact, the original punctuation is so odd (…— blah blah …), that I wonder whether Shirer had actually used brackets originally after all.