land mines also used, especially in the Middle East and the Balkans; the initial attempt on Archduke Franz Ferdinand's life was with a grenade. With heavy weapons, the rocket-propelled grenade (RPG) has become a useful tool given the popularity of armored cars (discussed below), and Israeli forces have pioneered the use of aircraft-mounted missiles, as well as the innovative use of explosive devices. A sniper with a precision rifle is often used in fictional assassinations. However, certain pragmatic difficulties attend long-range shooting, including finding a hidden shooting position with a clear line of sight, detailed advance knowledge of the intended victim's travel plans, the ability to identify the target at long range, and the ability to score a first-round lethal hit at long range, which is usually measured in hundreds of meters. A dedicated sniper rifle is also expensive, often costing thousands of dollars because of the high level of precision machining and handfinishing required to achieve extreme accuracy. Despite their comparative disadvantages, handguns are more easily concealable and so are much more commonly used than rifles. Of the 74 principal incidents evaluated in a major study about assassination attempts in the US in the second half of the 20th century, 51% were undertaken by a handgun, 30% with a rifle or shotgun, 15% used knives, and 8% explosives (the use of multiple weapons/methods was reported in 16% of all cases). In the case of state-sponsored assassination, poisoning can be more easily denied. Georgi Markov, a dissident from Bulgaria, was assassinated by ricin poisoning. A tiny pellet containing the poison was injected into his leg through a specially designed umbrella. Widespread allegations involving the Bulgarian government and the KGB have not led to any legal results. However, after the fall of the Soviet Union, it was learned that the KGB had developed an umbrella that could inject ricin pellets into a victim, and two former KGB agents who defected stated that the agency assisted in the murder. The CIA made several attempts to assassinate Fidel Castro; many of the schemes involving poisoning his cigars. In the late 1950s, the KGB assassin Bohdan Stashynsky killed Ukrainian nationalist leaders Lev Rebet and Stepan Bandera with a spray gun that fired a jet of poison gas from a crushed cyanide ampule, making their deaths look like heart attacks. A 2006 case in the UK concerned the assassination of Alexander Litvinenko who was given