The president of Poland, Andrzej Duda, has repeated his call for the US to base nuclear weapons on Polish soil. In the presidential palace in Warsaw, he told me that it would make Poland stronger and safer, as it faces Russia. Viewed from Poland, President Putin's Russia is a clear and a present danger. President Duda, who is also commander-in-chief of the rapidly expanding Polish armed forces, said today's Russia is at least as aggressive as the former Soviet Union. He condemned what he called Moscow's imperial greed.