Mezue ahịrịokwu na-esonụ: Na 28 June 1914 Archduke Franz Ferdinand nke Austria, onye nketa nke ocheeze Austro-Hungarian, gburu onye mba Bosnia Serb na Sarajevo, onye megidere ọchịchị Austria-Hungary
Mgbakwunye nke Bosnia-Herzegovina. Ọ bụghị na a pụghị izere ịlụ agha, ma ndị ndú, ndị nnọchiteanya mba na mba, na ndị ha na narị afọ nke iri na itoolu jikọrọ aka mere ka e nwee ọnọdụ ga-eme ka e nwee agha kpụ ọkụ n'ọnụ. Echiche nke Pan-Slavism na okpukperechi a na-ekerịta kere nkwenye siri ike n'etiti ọha na eze n'etiti Russia na Serbia. Esemokwu ókèala mere ka e nwee esemokwu n'etiti Germany na France nakwa n'etiti Austria-Hungary na Serbia, n'ihi ya kwa, e nwere njikọ ndị jikọrọ mba dị iche iche n'ebe nile na Europe. E guzobere netwọkụ nke Triple Entente na Triple Alliance tupu agha. Nicholas achọghị ịhapụ Serbia n'okpuru ultimatum nke Austria, ma ọ bụ kpalie agha zuru ụwa ọnụ. N'ọtụtụ akwụkwọ ozi ha na Wilhelm nke Germany (nke a na-akpọ "Willy<unk>Nicky correspondence") ha abụọ kwupụtara ọchịchọ ha maka udo, onye ọ bụla n'ime ha gbalịrị ime ka onye nke ọzọ laa azụ. Nicholas chọrọ ka e mee ka Russia jikọọ nanị megide Austria-Hungary, na-enwe olileanya igbochi agha na Germany.