Plan Dalet (Hebrew: תוכנית ד', Tokhnit dalet "Plan D"; 1 April – 14 May, 1948) was a Zionist military plan executed during the 1948 Palestine war for the conquest of territory in Mandatory Palestine in preparation for the establishment of a Jewish state. The plan was the blueprint for Israel's military operations, starting in March 1948 until the end of the war in early 1949, and so played a central role in the 1948 Palestinian expulsion and flight known as the Nakba. The plan was requested by the Jewish Agency leader and later first prime minister of Israel David Ben-Gurion, and developed by the Haganah and finalized on March 10, 1948. Historians describe Plan Dalet as the beginning of a new phase in the 1948 Palestine war in which Zionist forces shifted to an offensive strategy. The plan was a set of guidelines to take control of Mandatory Palestine, declare a Jewish state, and defend its borders and people, including the Jewish population outside of the borders, "before, and in anticipation of" the invasion by regular Arab armies. Plan Dalet specifically included gaining control of areas wherever Yishuv populations existed, including those outside the borders of the proposed Jewish state. The plan's tactics involved laying siege to Palestinian Arab villages, bombing neighbourhoods of cities, forced expulsion of their inhabitants, and setting fields and houses on fire and detonating TNT in the rubble to prevent any return. Zionist military units possessed detailed lists of neighborhoods and villages to be destroyed and their Arab inhabitants expelled. One of the first and most well known operations of Plan Dalet was the Deir Yassin massacre. This strategy is subject to controversy, with some historians characterizing it as defensive1, while others assert that it was an integral part of a planned strategy for the expulsion, sometimes called an ethnic cleansing, of the area's native inhabitants.