austria-hungary was outraged that the heir to their throne had been killed. they blamed serbia and bombed the capital, belgrade. the serbians tried to surrender, but austria-hungary bombed them anyway. serbia's ally, russia, then helped to defend it from attack. soon after, germany, austria-hungary's ally, declared war on russia as well as starting to move towards french territory, ready to invade, attacking belgium as they progressed. the french soldiers started to get ready for a german invasion. when germany declared war on france, then under the terms of the triple entente, britain then ordered germany to stop attacking belgium, who was neutral during the war. when the germans didn't retreat from belgium, britain declared war on germany. finally, austria-hungary declared war on russia and wwi commenced.