A cognate is a word in a language that is related to a word in another language. For instance, the word "night" is a cognate of the German "nacht" and more distantly of the French "nuit", itself descended from Latin "nux". The reconstructed Proto Indo European form is *nókʷts. Linguistics can treat words to some extent like evolutionary biologists treat genes, and if they understand the sound changes that happen in languages and their daughter languages they can come up with reconstructed forms of the ancestral word.

When linguists study a language family like Indo-European, they find some words are well preserved, taking sound changes into accounts. Words like horse, axle and wheel are among the most conserved words in the Indo-European languages, which has led to the hypothesis that before the Proto-Indo-European language began to break up, the Proto-Indo-Europeans had already domesticated horses and invented horse drawn chariots. Other linguistic evidence, such as conserved names for flora and fauna, give clues as to where these ancient people lived, and the Pontic-Caspian Steppe is a major candidate.

From there various groups spread, some south to Anatolia (the Hittites), Greece, others headed west (the Celts and Italic peoples), some north and are the likely ancestors of the Germanic peoples. Others went east and were the ancestors of the Indo-Iranian peoples. There were other groups that seemed to stay closer to home like the Balto-Slavic and Albanian peoples.

It's more complex than that, with influences from both related and unrelated languages (think about how many Romance words are in the English language, largely borrowings from Norman French).

It's an interesting way to use genetics to confirm what has been hinted by the linguistic evidence from Proto-Indo-European scholarship. In the Indo-European languages, some of the most conserved words across much of the language family have to do with horses and chariots, with cognates for horse, axle, wheel and related words to be found throughout the family. The Yamnaya are closely associated with the Proto-Indo-Europeans, and the Pontic-Caspian Steppe is often viewed as one of the more probable locations for the Proto-Indo-European urheimat.

Germany was permitted a civil defense force. It was explicitly forbidden an army offensive capabilities. The abolition of the General Staff was a critical part of that, because the senior officers in any army, the product of generations of training and experience, is something that would be extraordinarily hard to reproduce. The Allies didn't merely want to hamper Germany's ability to wage war, they wanted to actively terminate it. The Weimar government, by very quietly breaching the Treaty as regards to the General Staff, by calling them "civil servants" and then giving them the space and the time to pick up the pieces and begin planning for the next war, ultimately handed Hitler not only the expertise to wage another war, but the actual plans for waging that war.

Whether Nazism would have risen or not if Versailles had had easier terms is one history's great "what if" stories. What is clear, however, is that even the Weimar Republic was planning for a potential sequel to the Great War. One of the provisions of Versailles, the abolition of the Germany Army's General Staff, was secretly undermined by the Weimar government. The members of the General Staff were taken out of their uniforms, dressed up as civilian civil servants, put on the government payroll, and then spent the next decade planning the next war. When Hitler rose to power, he had a German Army; the high ranking officers, and all that was needed was the time to put the flesh on the bones.

Churchill's explanation was that the public sentiment in the Allied countries, and in particular in France, made it impossible for the Allied politicians and diplomats to do anything other than cut out pounds of flesh. A generation had been cut down in its prime, and the public weren't interested in nuance, only in punishment.

This is usually invoked as an explanation for the ill will many Germans had towards the Allies; feeling that they were being unfairly blamed and forced to pay for a war in which the other Great Powers had all played their own role in making inevitable.

When 800 years old you reach, look as good as her you will not!