But he said the fact that war was now `` unthinkable '' between the former World War Held in Belgian city of Brussels on anniversary of outbreak of World War I. Germany invaded neutral Belgium on August 4 , 1914 , and Britain declared war . Over the next four years , 16 million people died in the conflict , many on Belgian battlefields . Prince William said war was now ` ` unthinkable '' between nations who had fought .
Held in Belgian city of Brussels on anniversary of outbreak of World War I. Germany invaded neutral Belgium on August 4 , 1914 , and Britain declared war . Over the next four years , 16 million people died in the conflict , many on Belgian battlefields . Prince William said war was now ` ` unthinkable '' between nations who had fought .