The morning after the inventor's death, his nephew Sava Kosanovic´ hurried to his uncle's room at the Hotel New Yorker. He was an up-and-coming Yugoslav official with suspected connections to the communist party in his country. By the time he arrived, Tesla's body had already been removed, and Kosanovic´ suspected that someone had already gone through his uncle's effects. Technical papers were missing as well as a black notebook he knew Tesla kept—a notebook with several hundred pages, some of which were marked "Government."

P. E. Foxworth, assistant director of the New York FBI office, was called in to investigate. According to Foxworth, the government was "vitally interested" in preserving Tesla's papers. Two days after Tesla's death, representatives of the Office of Alien Property went to his room at the New Yorker Hotel and seized all his possessions.

Dr. John G. Trump, an electrical engineer with the National Defense Research Committee of the Office of Scientific Research and Development, was called in to analyze the Tesla papers in OAP custody. Following a three-day investigation, Dr. Trump concluded:

    His [Tesla's] thoughts and efforts during at least the past 15 years were primarily of a speculative, philosophical, and somewhat promotional character often concerned with the production and wireless transmission of power; but did not include new, sound, workable principles or methods for realizing such results. 

Just after World War II, there was a renewed interest in beam weapons. Copies of Tesla's papers on particle beam weaponry were sent to Patterson Air Force Base in Dayton, Ohio. An operation code-named "Project Nick" was heavily funded and placed under the command of Brigadier General L. C. Craigie to test the feasibility of Tesla's concept. Details of the experiments were never published, and the project was apparently discontinued. But something peculiar happened. The copies of Tesla's papers disappeared and nobody knows what happened to them.

In 1952, Tesla's remaining papers and possessions were released to Sava Kosanovic´ and returned to Belgrade, Yugoslavia where a museum was created in the inventor's honor. For many years, under Tito's communist regime, it was extremely difficult for Western journalists and scholars to gain access to the Tesla archive in Yugoslavia; even then they were allowed to see only selected papers. This was not the case for Soviet scientists who came in delegations during the 1950s. Concerns increased in 1960 when Soviet Premier Khrushchev announced to the Supreme Soviet that "a new and fantastic weapon was in the hatching stage."

Work on beam weapons also continued in the United States. In 1958 the Defense Advanced Research Projects Agency (DARPA) initiated a top-secret project code-named "Seesaw" at Lawrence Livermore Laboratory to develop a charged-particle beam weapon. More than ten years and twenty-seven million dollars later, the project was abandoned "because of the projected high costs associated with implementation as well as the formidable technical problems associated with propagating a beam through very long ranges in the atmosphere." Scientists associated with the project had no knowledge of Tesla's papers.

In the late 1970s, there was fear that the Soviets may have achieved a technological breakthrough. Some U.S. defense analysts concluded that a large beam weapon facility was under construction near the Sino-Soviet border in Southern Russia.

The American response to this "technological surprise" was the Strategic Defense Initiative announced by President Ronald Reagan in 1983. Teams of government scientists were urged to "turn their great talents now to the cause of mankind and world peace, to give us the means of rendering these nuclear weapons impotent and obsolete."

Today, after a half-century of research and billions of dollars of investment, the SDI program is generally considered a failure, and there is still no realistic means of defense against a nuclear missile attack.

Tesla's suite at the hotel New Yorker following his funeral on January 12, 1943. Left to right: Bogoljub Jevtic´, a member of the last Royal Government of the Kingdom of Yugoslavia; Professor Boris Furlan, a Slovene active during the war in the United States, who went back to Yugoslavia where he was arrested and liquidated brutally; Sava Kosanovic´, Tesla's nephew and member of the Royal Government in exile.
 

Articles in Tesla's hotel room after his death. Note cabinets and one of the invertor's safes. Three packages of Nabisco crackers can be seen on one of the upper shelves of the cabinet at left.
 

A model of Tesla's remote-controlled boat housed at the Tesla Museum in Belgrade, Yugoslavia.
 

The library archives at the Tesla Museum in Belgrade, Yugoslavia.
 

U.S. satellite reconnaissance photo of suspected Soviet beam weapon installation near Semipalatinsk. Published July 28, 1980. (Courtesy Aviation Week & Space Technology)
 

The death mask of Nikola Tesla in the offices of Gernsback Publications, New York City, in celebration of the Tesla centennial, June 25, 1956. The mask was heavily electroplated with copper, a process that took ten days, and was mounted on a marble-composition pedestal. Three medallions, executed in bas-relief on the base, commemorate Tesla's greatest inventions: the Tesla oscillation transformer, the first AC induction motor, and the tower for wireless power transmission.