The Austro-Hungarian Empire launched WWI, when it launched a war of aggression against Serbia. Since the First Lady of the US is a Slovene it is worth answering your slander regarding Serbs killing Slovenes, ignoring your other slanders. The Slovenian War of Independence started when Slovenian forces attacked forces of the Yugoslav People's Army stationed in Slovenia. These were not under the control of the Republic of Serbia; the Yugoslav Defence Minister at the time was a Yugoslav of mixed Serb and Croat ethnicity. There were only 19 Slovenians killed in the 10-day war. Serbs and Slovenes had good relations under Yugoslavia right up until near the end of the country. In spite of slanderers like you, the two peoples are likely to have good relations going forward.