The immediate cause of the first world war was the invasion of Austria on Serbia. The relations of Austria and Serbia kept deteriorating from 1908 which reached its peak by 1914. One of these organisations was ‘Black Hand’. This organisation together with another organisation ‘Organisation of death’, planned to assassinate the governor, petriach of Bosnia. But at this time, he came to know that the prince of Austria, Ferdinand was supposed to be on a government tour of Bosnia, then he conspired the murder. This murder was strongly condemned in Austria. Austria decided to inflict punishment on Serbia for the killing. The Austrian authorities thwarted the sovereignty demand for participation in the issue of Serbian cessesion. So they rejected the contention of Serbian plea as unsatisfactory and declared war against Serbia on July 28, 1914 CE.
