I assume that you are talking about the Balkan Wars of the early 1910s and the assassination of Archduke Franz Ferdinand. If so, the Balkan War led to the assassination because they inflamed Slavic nationalism and hatred of Austria-Hungary.
The Balkan Wars mattered because Serbia was using these wars to take more territory, in particular a port on the Adriatic Sea (access to the ocean is very important for economic and military reasons). Austria did not want Serbia to get these territories. After the wars, Austria (with help from other European nations) forced Serbia to give up the territories it had gained. These actions made Serbia (and the Slavs in the region who identified with Serbia because it was a Slavic country) very angry at Austria. This anger led to the killing of the Austrian Archduke.