MOSCOW--Until a week ago, Alexander Litvinenko, a former colonel in the Russian Federal Security Service, the FSB, was virtually unknown outside the murky world of Russian intelligence. With his death in London from a massive dose of the radioactive element polonium 210, however, his fate may lead to a fundamentally different relationship between Russia and the West. Beginning with the Yeltsin era, two U.S. administrations have muted their criticism of Russia. This was the case even in the face of a series of political murders in Russia. But if Litvinenko, a British subject, was murdered by Russian intelligence on British...