Members of the Irgun came mostly from Betar and from the Revisionist Party both in Palestine and abroad. The Revisionist Movement made up a popular backing for the underground organization. Ze'ev Jabotinsky, founder of Revisionist Zionism, commanded the organization until he died in 1940. He formulated the general realm of operation, regarding "Restraint" and the end thereof, and was the inspiration for the organization overall. An additional major source of ideological inspiration was the poetry of Uri Zvi Greenberg. The symbol of the organization, with the motto רק כך (only thus), underneath a hand holding a rifle in the foreground of a map showing both Mandatory Palestine and the Emirate of Transjordan (at the time, both were administered under the terms of the British Mandate for Palestine), implied that force was the only way to "liberate the homeland."