Sarah Aaronsohn, her brother Aaron, and their friend Avshalom Feinberg formed and directed Nili. According to Chaim Herzog, the Aaronsohns were motivated to assist the British after witnessing genocidal acts against the Armenians by the Turks.
Sarah oversaw operations in Zichron Yaakov. She passed their information to British agents who entered Zichron Yaakov by boat, or sometimes brought it personally to the British in Egypt.
In the fall of 1917, the Turks discovered Nili's operations and began rolling up their spy network. In September of that year they surrounded Zichron Yaakov and captured Sarah, whom they interrogated for three or four days using torture. At the end of that time Sarah killed herself to avoid further torture, and Nili's operations ceased.