States, Yugoslavia, Turkey, and Dutch Indonesia. Switzerland protected British interests in Germany, France, Italy, Hungary, Romania and Japan. It protected Vichy France's interests in Britain, the United States, Italy, Egypt and Brazil. It protected Italy's interest in Egypt and Brazil. It protected the United States interest in Germany, France, Italy, Japan, China and Denmark. It protected Japan's interest in Britain the United States, Egypt and Argentina. The diplomats arranged travel permissions, helping tens of thousands of people to return to their home countries after being trapped in an enemy nation. Swiss diplomats also supervised closed enemy embassies. Of special importance was the protection provided prisoners of war, especially the sick and wounded. Service of Intellectual Assistance to Prisoners of War (SIAP) In 1939, the Service of Intellectual Assistance to Prisoners of War (SIAP) was created by the International Bureau of Education (IBE), a Geneva-based international organization dedicated to educational matters. In collaboration with the Swiss Federal Council, who initially funded the project, and the International Committee of the Red Cross (ICRC), the SIAP provided over half a million books to prisoners of war during World War II, and organized educational opportunities and study groups in prison camps. Financial relationships with Nazi Germany Switzerland's trade was blockaded by both the Allies and by the Axis. Each side openly exerted pressure on Switzerland not to trade with the other. Economic cooperation and extension of credit to the Third Reich varied according to the perceived likelihood of invasion, and the availability of other trading partners. Concessions reached their zenith after a crucial rail link through Vichy France was severed in 1942, leaving Switzerland completely surrounded by the Axis. Switzerland relied on trade for half of its food and essentially all of its fuel; however, the Swiss controlled vital trans-alpine rail tunnels between Germany and Italy and possessed considerable electrical generating capacity that was relatively safe from air attack. Switzerland's most important exports during the war were precision machine tools, watches, jewel bearings (used in bomb sights), electricity, and dairy products. Until 1936, the Swiss franc was the only remaining major freely convertible currency in the world, and both the Allies and the Germans sold large amounts of gold to the Swiss National Bank. Between 1940 and 1945, the German Reichsbank sold 1.3 billion francs (approximately 18 billion francs adjusted for inflation to 2019) worth of gold to Swiss banks in exchange for Swiss