Germany invaded Belgium on August 4, 1914, helping bring Britain into World War I.
Germany’s invasion was part of the Schlieffen Plan, which aimed to defeat France quickly by sending German armies through neutral Belgium before turning east against Russia. Belgium had declared that it would defend its neutrality, and its government rejected Germany’s demand for military passage.
Belgian neutrality had been internationally recognized by the 1839 Treaty of London. Britain viewed the German invasion as a violation of that treaty and issued an ultimatum demanding that Germany withdraw. When Germany refused, Britain declared war on Germany late on August 4.
The invasion began with the attack on Liège, whose fortified defenses delayed the German advance. German forces soon occupied Brussels and much of Belgium, while reports of violence against civilians became known as the “Rape of Belgium.” The country’s invasion, rather than an attack on Britain itself, was the immediate reason Britain entered the war.