not have the resources to support it. On 20 May 1944, the Maquis du Mont Mouchet in the Massif Central staged an open uprising on its own initiative and was crushed within three weeks with the usual reprisals. Despite this, on 6 June, broadcast an impassioned call to arms to the French people on the BBC, which the maquisards interpreted as a signal for overt action; a lower-key message from Eisenhower to avoid a "premature uprising" was widely ignored. As a direct consequence, in July the 4,000 FFI on the Vercors Plateau near Grenoble were attacked by a German force of 10,000 including paratroopers and troops in gliders. In the Battle of Vercors, the lightly armed French defences were overwhelmed, despite assistance from Allied agents, air-drops and special forces. Allied military policy Military strategy for the war as a whole was discussed among the Big Three powers, and especially among the United Kingdom and the United States, who were especially close, with numerous calls and meetings held between U.S. President Franklin D. Roosevelt and British Prime Minister Winston Churchill. In addition, the leaders of the Big Three met at conferences during the war to decide on overall military strategy. The Arcadia Conference held in Washington, D.C. from December 22, 1941, to January 14, 1942, followed the American and the British declarations of war on Japan; Japan's allies, Germany and Italy, declared war on the United States. The main policy decisions of Arcadia included the "Germany First" (also known as "Europe first") policy that the defeat of Germany had higher priority than the war with Japan. The Second Washington Conference in June 1942 confirmed a decision not to open a second front in France but to first invade French North Africa as part of a joint Mediterranean strategy for an attack on Italy (described as the "soft under-belly" of the Axis). The decision to undertake a cross-channel invasion in 1944 was taken at the Trident Conference in Washington in May 1943. General Eisenhower was appointed commander of SHAEF and General Bernard Montgomery was named as commander of the 21st Army Group, which comprised all the land forces involved in the invasion. The coast of Normandy in northwestern France was chosen as the site of the invasion. The Tehran Conference (28 November to 1 December 1943) a strategy meeting of the Big Three leaders Joseph Stalin, Franklin D. Roosevelt and Winston Churchill