Both Belgium and occupied northern France were badly mistreated by Germany in War I. Hew Strachan brings it up in his study of War I.
The following two books might shed some light on the subject, if you're interested:
Belgium and the First World War by Henri Perrine
'Except for a thin slice of territory south of the Yser River, Belgium was entirely occupied by the Germans from October 15, 1914 until the end of the First World War. The suffering of the Belgian people, which made such a vivid impression on Americans, British, Canadians, and Australians at the time, has been largely forgotten. The invasion was accompanied by mass executions and wholesale arson; nearly 6,000 civilians were killed. Over 2 million Belgians escaped to the Netherlands, France, and Britain. When order was restored, the nation faced a grave economic crisis. A major exporter and among the most prosperous countries in Europe, Belgium was now cut off from its supplies of raw material and its markets, and subject to heavy war taxes, fines, and requisitions. As Germany began increasingly to feel the effects of the Allied blockade, the temptation grew to exploit to the hilt all Belgian resources, including labor. With eloquence and passion, the eminent medievalist Henri Pirenne (1862-1935) describes the hunger, the deprivations, the unemployment, the arbitrary arrests and deportations, the indignities of home invasions and confiscations, the censorship, the conscription of workers, the dismantling and destruction of Belgian factories, and the administrative division of the country. Belgium and the First World War comprehensively surveys the catastrophe and chronicles the stoicism and the resiliency with which Belgians responded.'
The Rape of Belgium: The Untold Story of World War I by Larry Zuckerman
'In August 1914, the German Army invaded the neutral nation of Belgium, violating a treaty that the German chancellor dismissed as a "scrap of paper." The invaders terrorized the Belgians, shooting thousands of civilians and looting and burning scores of towns, including Louvain, which housed the country's preeminent university.
The Rape of Belgium recalls the bloodshed and destruction of the 1914 invasion, and the outrage it inspired abroad. Yet Larry Zuckerman does not stop there, and takes us on a harrowing journey over the next fifty months, vividly documenting Germany's occupation of Belgium. The occupiers plundered the country, looting its rich supply of natural resources; deporting Belgians en masse to Germany and northern France as forced laborers; and jailing thousands on contrived charges, including the failure to inform on family or neighbors. Despite the duration of the siege and the destruction left in its wake, in considering Belgium, neither the Allies nor the history books focused on the occupation, and instead cast their attention almost wholly on the invasion.
Now, The Rape of Belgium draws on a little-known story to remind us of the horrors of war. Further, Zuckerman shows why the Allies refrained from punishing the Germans for the occupation and controversially suggests that had the victors followed through, Europe's reaction to the rise of Nazi Germany might have taken a very different course.'
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