Stalin married Kato Svanidze in a church ceremony at Senaki in July 1906. In March 1907 she bore a son, Yakov. By that year — according to the historian Robert Service — Stalin had established himself as "Georgia's leading Bolshevik". He attended the Fifth RSDLP Congress, held in London in May–June 1907. After returning to Tiflis, Stalin organised the robbing of a large delivery of money to the Imperial Bank in June 1907. His gang ambushed the armed convoy in Yerevan Square with gunfire and home-made bombs. Around 40 people were killed, but all of his gang escaped alive.