Israel's objectives for the war were originally based on the Haganah's 1946 Plan and run by David Ben-Gurion. The plan called for the rapid build-up of forces to fight against what the army saw as the greatest threat: invasion from the many Arab states. By using the 1946 Plan, Ben-Gurion hoped to secure the land given to Israel in the UN Partition Plan. As the war went on, the goals changed slightly with the introduction in March 1948 of Plan Dalet (Plan D). Instead of simply holding the lands given to Israel, the plan now commanded Israel's forces to work remove Arabs from Jewish-controlled land, defend Jewish settlements in Arab Palestine, and to take Arab land at particular positions for a strategic advantage. A possible reason for the change is given by historian David Tal, who points out that it was probably a response to the stiffer resistance from Palestinians and a general desire to put Israeli forces in the most defensible positions. Yet, as Tal also points out, this strategic plan has never been without some controversy, particularly the part of the plan which forced Palestinian movement.