Formed a mere two months after the Bolshevik Revolution, the Cheka, the Soviet Security and Intelligence Agency, was formed to gather intelligence and promote revolution abroad. This organisation underwent a series of transformations over the following decades and achieved some remarkable successes against Nazi Germany, Imperial Japan, the USA, and the United Kingdom. Throughout the 1930s, the Soviets pursued their ambition of gaining influence in Eastern Europe. It was a plan that inevitably brought them into conflict with Nazi Germany, against which they began setting up clandestine organisations that were meant to become operational in the event of war. The USA had been of peripheral interest to the Soviets up until the prospect of war loomed ever closer. Then, when it became known that Britain and the USA were exploring the potential of atomic weapons, espionage in the western hemisphere became of paramount importance. Despite their being allies against the Nazis, the Soviets significantly increased spying activity against both nations in an effort to develop their own atomic bomb programme. After the end of the Second World War, a new and ominous threat hung over the world in the guise of the Cold War when the Soviets brought into play their British spy network which became known as the Cambridge Five. These were agents who had been radicalised and recruited during the 1930s and then embedded within the British security services. In Stalin’s Top Spies the author explores five of the Soviet Union’s greatest spies: Leopold Trepper (and the Red Orchestra), Ursula Kuczynski (the Atomic Spy), Richard Sorge (a Soviet agent in Tokyo), Kim Philby (the Cambridge Spy), and Rudolf Abel (a Soviet intelligence officer who was arrested in the USA on charges of espionage in 1957). The book not only reveals their successes and failures, but assessing the extent to which they influenced world events from the Second World War through to the early years of the Cold War. In so doing, it also highlights the failures of the target nations to recognise the threat posed to them and exposes their lack of success in dealing with it.