„In retrospect, it is easy to see that Hitler's successful gamble in the Rhineland brought him a victory more staggering and more fatal in its immense consequences than could be comprehended at the time. At home it fortified his popularity and his power, raising them to heights which no German ruler of the past had ever enjoyed. It assured his ascendancy over his generals, who had hesitated and weakened at a moment of crisis when he had held firm. It taught them that in foreign politics and even in military affairs his judgment was superior to theirs. They had feared that the French would fight; he knew better. And finally, and above all, the Rhineland occupation, small as it was as a military operation, opened the way, as only Hitler (and Churchill, alone, in England) seemed to realize, to vast new opportunities in a Europe which was not only shaken but whose strategic situation was irrevocably changed by the parading of three German battalions across the Rhine bridges.
Conversely, it is equally easy to see, in retrospect, that France's failure to repel the Wehrmacht battalions and Britain's failure to back her in what would have been nothing more than a police action was a disaster for the West from which sprang all the later ones of even greater magnitude. In March 1936 the two Western democracies were given their last chance to halt, without the risk of a serious war, the rise of a militarized, aggressive, totalitarian Germany and, in fact - as we have seen Hitler admitting - bring the Nazi dictator and his regime tumbling down. They let the chance slip by.
For France, it was the beginning of the end. Her allies in the East, Russia, Poland, Czechoslovakia, Rumania and Yugoslavia, suddenly were faced with the fact that France would not fight against German aggression to preserve the security system which the French government itself had taken the lead in so laboriously building up. But more than that. These Eastern allies began to realize that even if France were not so supine, she would soon not be able to lend them much assistance because of Germany's feverish construction of a West Wall behind the Franco-German border. The erection of this fortress line, they saw, would quickly change the strategic map of Europe, to their detriment. They could scarcely expect a France which did not dare, with her one hundred divisions, to repel three German battalions, to bleed her young manhood against impregnable German fortifications which the Wehrmacht attacked in the East. But even if the unexpected took place, it would be futile. Henceforth the French could tie down in the West only a small part of the growing German Army. The rest would be free for operations against Germany's Eastern neighbors.“
The Rise and Fall of the Third Reich: A History of Nazi Germany