The Western European Enlightenment in the 18th century influenced the initiation of a national awakening of Bulgaria. It restored national consciousness and provided an ideological basis for the liberation struggle, resulting in the 1876 April Uprising. Up to 30,000 Bulgarians were killed as Ottoman authorities put down the rebellion. The massacres prompted the Great Powers to take action. They convened the Constantinople Conference in 1876, but their decisions were rejected by the Ottomans. This allowed the Russian Empire to seek a military solution without risking confrontation with other Great Powers, as had happened in the Crimean War. In 1877 Russia declared war on the Ottomans and defeated them with the help of Bulgarian rebels, particularly during the crucial Battle of Shipka Pass which secured Russian control over the main road to Constantinople.