The assassin was Gavrilo Princip of the Serbian society The Black Hand, a terrorist organization. The Serbian government was cognizant of the plot; the world generally was outraged. July 23. Austrian ultimatum to Belgrade (48 hours). July 28. AUSTRIA DECLARED WAR ON SERBIA. Belgrade was bombarded the next day, though Austria was not ready for real operations until about August 12. The declaration of war was meant to create a fait accompli. July 29. The Russian tsar agreed to general mobilization. July 31. Germany proclaimed "state of threatening danger of war." Sent a 12-hour ultimatum to Russia demanding cessation of preparations on the German frontier. Germany refused a British request that the neutrality of Belgium be respected.