From 1933 to 1939, as he greatly expanded the scope of the federal government's policies and powers in response to the Great Depression, President Roosevelt relied on his famous 'Brain Trust' of top advisers. Although working directly for the president, they were often appointed to vacant positions in federal agencies and departments, whence they drew their salaries since the White House lacked statutory or budgetary authority to create staff positions. It was not until 1939, during Roosevelt's second term in office, that the foundations of the modern White House staff were created using a formal structure. Roosevelt was able to persuade Congress to approve the creation of the Executive Office of the President, which would report directly to the president. During World War II, Roosevelt created the position of "Chief of Staff to the Commander-in-Chief" for his principal military adviser, Fleet Admiral William D. Leahy.