Causes of World War I

“The video mentions that Austria-Hungary had an alliance with Germany. If Austria-Hungary decided to declare war on Serbia after the assassination, how might this alliance with Germany affect the situation? Imagine Germany promised to support Austria-Hungary if Austria-Hungary took action against Serbia. How could this promise, based on their alliance, make Austria-Hungary more likely to declare war? If other countries had alliances with Serbia, how might Austria-Hungary's alliance with Germany make the situation more complicated and potentially lead to a larger conflict?”