For more than four years during the First World War Belgium was almost completely occupied. In response to the brutal occupation of the country, while many Belgian Jews were in the army, some played a more or less important role by various kinds of effective or spiritual resistance. A few others collaborated with the enemy. 'The soul of the moral resistance' was Chief Rabbi Armand Bloch (1861–1923), a man who was quiet by nature, but who put himself in danger; among other things, he delivered a sermon on the first day of Passover 1916 that would bring him, in May, in front of the War Council, which sentenced him 'for insult' to a six-month prison term. By describing his career and analysing his published works, this article will try to understand his reasons for resistance.