Question: When World War II started, who was the leader of the country where the Battle of Riva Ridge was fought?

full_context: Document 1: Alps: By 1940 the Third Reich had occupied many of the Alpine countries. Austria underwent a political coup that made it part of the Third Reich; France had been invaded and Italy was a fascist regime. Switzerland was the only country to luckily avoid invasion. The Swiss Confederate mobilized its troops—the country follows the doctrine of "armed neutrality" with all males required to have military training—a number that General Eisenhower estimated to be about 850,000. The Swiss commanders wired the infrastructure leading into the country, and threatening to destroy bridges, railway tunnels and passes in the event of a Nazi invasion, and then they retreated to the heart of the mountain peaks where conditions were harsher and a military invasion would involve difficult and protracted battles.
Document 2: Southern Europe: Italy became a major industrialized country again, due to its post-war economic miracle. The European Union (EU) involved the division of powers, with taxation, health and education handled by the nation states, while the EU had charge of market rules, competition, legal standards and environmentalism. The Soviet economic and political system collapsed, leading to the end of communism in the satellite countries in 1989, and the dissolution of the Soviet Union itself in 1991. As a consequence, Europe's integration deepened, the continent became depolarised, and the European Union expanded to subsequently include many of the formerly communist European countries – Romania and Bulgaria (2007) and Croatia (2013).
Document 3: Great power: When World War II started in 1939, it divided the world into two alliances—the Allies (the United Kingdom and France at first in Europe, China in Asia since 1937, followed in 1941 by the Soviet Union, the United States); and the Axis powers consisting of Germany, Italy and Japan.[nb 1] During World War II, the United States, United Kingdom, and Soviet Union controlled Allied policy and emerged as the "Big Three". The Republic of China and the Big Three were referred as a "trusteeship of the powerful"  and were recognized as the Allied "Big Four" in Declaration by United Nations in 1942. These four countries were referred as the "Four Policemen" of the Allies and considered as the primary victors of World War II. The importance of France was acknowledged by their inclusion, along with the other four, in the group of countries allotted permanent seats in the United Nations Security Council.
Document 4: Alpine Fortress: The Alpine Fortress () or Alpine Redoubt was the World War II national redoubt planned by Heinrich Himmler in November and December 1943 for Germany's government and armed forces to retreat to an area from "southern Bavaria across western Austria to northern Italy". The plan was never fully endorsed by Hitler and no serious attempt was made to put the plan into operation, although it would serve as an effective tool of propaganda and military deception by the Germans in the final stages of the war.
Document 5: Alps: Ski troops were trained for the war, and battles were waged in mountainous areas such as the battle at Riva Ridge in Italy, where the American 10th Mountain Division encountered heavy resistance in February 1945. At the end of the war, a substantial amount of Nazi plunder was found stored in Austria, where Hitler had hoped to retreat as the war drew to a close. The salt mines surrounding the Altaussee area, where American troops found 75 kilos of gold coins stored in a single mine, were used to store looted art, jewels, and currency; vast quantities of looted art were found and returned to the owners.
Document 6: Alatsee: Alatsee is a meromictic lake in Ostallgäu, Bavaria, Germany. At an elevation of 868.0 m, its surface area is 12.00 ha. This lake supposedly holds "Hitler's gold". Many divers have died or disappeared mysteriously in this lake due to the toxicity of the organisms living in this lake. These organisms create the "blood cloud " that occurs quite abundantly throughout the year.
Document 7: Alps: A mummified man, determined to be 5,000 years old, was discovered on a glacier at the Austrian–Italian border in 1991. By the 6th century BC, the Celtic La Tène culture was well established. Hannibal famously crossed the Alps with a herd of elephants, and the Romans had settlements in the region. In 1800 Napoleon crossed one of the mountain passes with an army of 40,000. The 18th and 19th centuries saw an influx of naturalists, writers, and artists, in particular the Romantics, followed by the golden age of alpinism as mountaineers began to ascend the peaks. In World War II, Adolf Hitler kept a base of operation in the Bavarian Alps throughout the war.
Document 8: Battle of Stalingrad: Bitter fighting raged for every ruin, street, factory, house, basement, and staircase. Even the sewers were the sites of firefights. The Germans called this unseen urban warfare Rattenkrieg ("Rat War"), and bitterly joked about capturing the kitchen but still fighting for the living room and the bedroom. Buildings had to be cleared room by room through the bombed-out debris of residential neighborhoods, office blocks, basements and apartment high-rises. Some of the taller buildings, blasted into roofless shells by earlier German aerial bombardment, saw floor-by-floor, close quarters combat, with the Germans and Soviets on alternate levels, firing at each other through holes in the floors. Fighting on and around Mamayev Kurgan, a prominent hill above the city, was particularly merciless; indeed, the position changed hands many times.
Document 9: Southern Europe: The Nazi regime under Adolf Hitler came to power in 1933, and along with Mussolini's Italy sought to gain control of the continent by the Second World War. Following the Allied victory in the Second World War, Europe was divided by the Iron Curtain. The countries in Southeastern Europe were dominated by the Soviet Union and became communist states. The major non-communist Southern European countries joined a US-led military alliance (NATO) and formed the European Economic Community amongst themselves. The countries in the Soviet sphere of influence joined the military alliance known as the Warsaw Pact and the economic bloc called Comecon. Yugoslavia was neutal.
Document 10: Modern history: After World War II, Europe was informally split into Western and Soviet spheres of influence. Western Europe later aligned as the North Atlantic Treaty Organization (NATO) and Eastern Europe as the Warsaw Pact. There was a shift in power from Western Europe and the British Empire to the two new superpowers, the United States and the Soviet Union. These two rivals would later face off in the Cold War. In Asia, the defeat of Japan led to its democratization. China's civil war continued through and after the war, resulting eventually in the establishment of the People's Republic of China. The former colonies of the European powers began their road to independence.
Document 11: World War II: The Empire of Japan aimed to dominate Asia and the Pacific and was already at war with the Republic of China in 1937, but the world war is generally said to have begun on 1 September 1939 with the invasion of Poland by Nazi Germany and subsequent declarations of war on Germany by France and the United Kingdom. Supplied by the Soviet Union, from late 1939 to early 1941, in a series of campaigns and treaties, Germany conquered or controlled much of continental Europe, and formed the Axis alliance with Italy and Japan. Under the Molotov -- Ribbentrop Pact of August 1939, Germany and the Soviet Union partitioned and annexed territories of their European neighbours, Poland, Finland, Romania and the Baltic states. The war continued primarily between the European Axis powers and the coalition of the United Kingdom and the British Commonwealth, with campaigns including the North Africa and East Africa campaigns, the aerial Battle of Britain, the Blitz bombing campaign, and the Balkan Campaign, as well as the long - running Battle of the Atlantic. On 22 June 1941, the European Axis powers launched an invasion of the Soviet Union, opening the largest land theatre of war in history, which trapped the major part of the Axis military forces into a war of attrition. In December 1941, Japan attacked the United States and European colonies in the Pacific Ocean, and quickly conquered much of the Western Pacific.
Document 12: Alps: Austrian-born Adolf Hitler had a lifelong romantic fascination with the Alps and by the 1930s established a home in the Obersalzberg region outside of Berchtesgaden. His first visit to the area was in 1923 and he maintained a strong tie there until the end of his life. At the end of World War II the US Army occupied Obersalzberg, to prevent Hitler from retreating with the Wehrmacht into the mountains.
Document 13: Warsaw Pact: On 23 October 1954 – only nine years after Allies (UK, USA and USSR) defeated Nazi Germany ending World War II in Europe – the admission of the Federal Republic of Germany to the North Atlantic Pact was finally decided. The incorporation of West Germany into the organization on 9 May 1955 was described as "a decisive turning point in the history of our continent" by Halvard Lange, Foreign Affairs Minister of Norway at the time. In November 1954, the USSR requested a new European Security Treaty, in order to make a final attempt to not have a remilitarized West Germany potentially opposed to the Soviet Union, with no success.
Document 14: Alps: Celtic tribes settled in Switzerland between 1000 to 1500 BC. The Raetians lived in the eastern regions, while the west was occupied by the Helvetii and the Allobrogi settled in the Rhone valley and in Savoy. Among the many substances Celtic tribes mined was salt in areas such as Salzburg in Austria where evidence of the Hallstatt culture was found by a mine manager in the 19th century. By the 6th century BC the La Tène culture was well established in the region, and became known for high quality decorated weapons and jewelry. The Celts were the most widespread of the mountain tribes—they had warriors that were strong, tall and fair skinned skilled with iron weapons, which gave them an advantage in warfare.
Document 15: Modern history: The Soviet Union created the Eastern Bloc of countries that it occupied, annexing some as Soviet Socialist Republics and maintaining others as satellite states that would later form the Warsaw Pact. The United States and various western European countries began a policy of "containment" of communism and forged myriad alliances to this end, including NATO. Several of these western countries also coordinated efforts regarding the rebuilding of western Europe, including western Germany, which the Soviets opposed. In other regions of the world, such as Latin America and Southeast Asia, the Soviet Union fostered communist revolutionary movements, which the United States and many of its allies opposed and, in some cases, attempted to "roll back". Many countries were prompted to align themselves with the nations that would later form either NATO or the Warsaw Pact, though other movements would also emerge.
ground_truth: Mussolini
sub_queries: Where was the battle at Riva Ridge? Answer: Italy
Who was the leader of Italy when World War II started? Answer: Mussolini