BERLIN — A World War II murder mystery featuring Winston Churchill, the British double agent Kim Philby, and Joseph Stalin could be solved after the Polish government called for the body of a national hero to be exhumed.

The leader of Poland’s wartime government in exile, General Wladyslaw Sikorski, died 65 years ago this month when his plane plunged into the sea off Gibraltar.

A British inquiry in 1943 found that the crash was caused by the plane’s controls jamming. But rumors persist of a plot to kill Sikorski, whose defence of the Polish national cause threatened to derail Britain’s relationship with the Soviet Union.

Now Poland’s president, Lech Kaczynski, and prime minister, Donald Tusk, have demanded that Sikorski’s body be exhumed from its tomb in Wawel Cathedral in Krakow, the traditional burial place of Polish heroes. “The tragic circumstances of the death of General Sikorski should be explained,” the president said.

Moves to exhume Sikorski’s body follow a long campaign by Polish historians, who claim that the general’s body was not examined properly before burial. They claim that he may already have been killed before the crash, in which his daughter also died, and only the pilot survived. In particular, they want an examination of his skull to see whether he was shot.

The general’s death has attracted a swarm of conspiracy theories that variously accuse British, Soviet, and even rival Polish factions of orchestrating his murder. But the most insistent rumors suggest that his death was ordered by the Soviet leader Stalin, incensed by Sikorski’s demand for an investigation into the Katyn massacre of Polish officers by Soviet troops. Stalin’s accusers claim that Sikorski’s plane was left unguarded on the runway at Gibraltar, and could easily have been sabotaged. They also point out that on the day of the crash, July 4, 1943, a plane carrying the Soviet ambassador Ivan Maisky and a small retinue of Soviet troops parked next to the doomed Polish leader’s unguarded aircraft.