On August 4 1914 German forces entered neutral Belgium - a decision that brought Britain to war in defence of international law bound by strategic interests and moral force.

The subsequent atrocities committed in Belgium & Northern France in those first weeks transformed many people's understandings of what was now at stake. The war now defined as a great moral cause, civilization versus German Kultur.

The 'rape' of Belgium caused international outrage and created a long propaganda war for the hearts and minds of millions overseas. At home ordinary Britons identified strongly with the Belgian plight with hundreds of thousands of refugees arriving on our shores. The German policy of civilian bombing raids and later unrestricted submarine warfare brought the shock of war to people's homes and further shaped our ideas of the bestial Hun.

The greatest atrocity of war was war itself. In the turbulent years of peace after 1918 the wartime motivations and meanings of the war for millions was refracted through the prism of post war disillusionment - so much so that a powerful counter myth set in by the late 1920's that has largely persisted. Many now felt that the British public and millions more were essentially manipulated by their governments to wage a pointless war of slaughter, and that the atrocities were at best hysterical stories ruthlessly transformed into motivational propaganda.

Michael Portillo explores the true history of those events in Belgium, the impact on people during wartime and the battle for meaning that followed.

Producer: Mark Burman.