war the size of the detail grew until it reached 16 agents and 2 supervisors by 1939. World War II created new and greater protection problems, especially those arising from the President's trips abroad to the Grand Strategy Conferences in such places as Casablanca, Quebec, Tehran, Cairo, and Yalta. To meet the increased demands, the White House detail was increased to 37 men early in the war.51

The volume of mail received by the White House had always been large, but it reached huge proportions under Franklin D. Roosevelt. Presidents had always received threatening letters but never in such quantities. To deal with this growing problem, the Secret Service established in 1940 the Protective Research Section to analyze and make available to those charged with protecting the President, information from White House mail and other sources concerning people potentially capable of violence to the President. The Protective Research Section undoubtedly permitted the Secret Service to anticipate and forestall many incidents that might have been embarrassing or harmful to the President.52

Although there was no advance warning of the attempt on Harry S. Truman's life on November 1, 1950, the protective measures taken by the Secret Service availed, and the assassins never succeeded in firing directly at the President. The assassins--Oscar Collazo and Griselio Torresola, Puerto Rican Nationalists living in New York-- tried to force their way into Blair House, at the time the President's residence while the white House was being repaired. Blair House was guarded by white House policemen and Secret Service agents. In the ensuing gun battle, Torresola and one White House policeman were killed, and Collazo and two White House policemen were wounded. Had the assassins succeeded in entering the front door of Blair House, they Would probably have been cut down immediately by another Secret Service agent inside who kept the doorway covered with a submachine gun from his vantage point at the foot of the main stairs. In all, some 27 shots were fired in less than 3 minutes.53

Collazo was brought to trial in 1951 and sentenced to death, but President Truman commuted the sentence to life imprisonment on July 24, 1952. Although there was a great deal of evidence linking Collazo and Torresola to the Nationalist Party of Puerto Rico and its leader, Pedro Albizu Campos, the Government could not establish that the attack on the President was part of a larger Nationalist conspiracy.54

The attack on President Truman led to the enactment in 1951 of legislation that permanently authorized the Secret Service to protect the President, his immediate family, the .President-elect, and the Vice President, the last upon his request. Protection of the Vice President by the Secret Service had begun in January 1945 when Harry S. Truman occupied the office.55

In 1962 Congress further enlarged the list of Government officers to be safeguarded, authorizing protection of the Vice President (or the officer next in order of succession to the Presidency) without requiring his request therefor; of the Vice President-elect; and of a