This page of the Primary However, that was exactly what caused the British to enter the war. Alliances were a major cause of the conflicts between countries in WW1 The original disagreement was between Serbia and Austria-Hungry over the assassination of Arch Duke Franz Ferdinand. After Archduke Franz Ferdinand, the heir to the Austrian throne was assassinated by a Serbian national, the alliance system that was in place was put into effect. Corrections? Ihre Dienstleistung! After Archduke Franz Ferdinand, the heir to the Austrian throne, was assassinated by a Serbian national, the alliance system that was in place was put into effect. with Russia to lapse in 1890. The most direct cause was the assassination of Austria-Hungary's Archduke on June 28, 1914. //