Austria-Hungary blamed Serbia for the assassination. Germany supported Austria-Hungary and promised full support should it come to war. Austria-Hungary sent a July Ultimatum to Serbia, listing 10 very strict rules they would have to agree to. Many historians think that Austria-Hungary already wanted a war with Serbia. Serbia agreed to most of the ten rules on the list, but not all of them. Austria-Hungary then declared war on Serbia. This quickly led to a full-scale war. Both countries' allies became involved in the war in a matter of days.