 Some observers, however, argue that other factors are at play, including improved intelligence-gathering leading to more arrests, and the construction of the Israeli West Bank barrier which has made it more difficult for terrorists to infiltrate.In 1943, the United States military used knowledge from decoded transmissions to carry out a targeted killing of the Japanese Admiral Isoroku Yamamoto.During the Cold War, the U.S. attempted several times to assassinate Cuban President Fidel Castro.