Frequent infighting, together with Napoleon's invasion of Russia in 1812, weakened the rebels, and the Ottomans were able to reverse many of their gains. Karađorđe was forced to flee Serbia in October 1813 and Belgrade fell later that month, bringing the First Serbian Uprising to a close. He and his followers sought refuge in the Austrian Empire, but were arrested and detained. Despite Ottoman requests for his extradition, the Austrians handed Karađorđe over to the Russians, who offered him refuge in Bessarabia. There, he joined the Greek secret society known as "Filiki Eteria", which planned to launch a pan-Balkan uprising against the Ottomans. Karađorđe returned to Serbia in secret in July 1817, but was killed shortly thereafter by agents of Miloš Obrenović, a rival rebel leader, who was concerned that Karađorđe's reappearance would cause the Ottomans to renege on the concessions they had agreed to following the Second Serbian Uprising of 1815. Karađorđe is considered the founder of the Karađorđević dynasty, which ruled Serbia in several intervals during the 19th and 20th centuries. His murder resulted in a violent, decades-long feud between his descendants and those of Obrenović, with the Serbian throne changing hands several times.