Whole books have been written on that subject. Hillsdale's president, Dr. Larry Arnn, has published a fine one (Churchill's Trial) on how Churchill contemplated the nature of mankind and resolved social needs with constitutional liberty.
Two qualities of leadership stand out: his ability to pursue the paramount goal to the exclusion of all others; and his ability to communicate. In the depths of 1940, he was the only possible choice for premier, because for almost a decade he had emphasized Nazi Germany as the primary threat, despite his understanding of communism. When Hitler invaded Russia he pledged immediate aid to Stalin: "If Hitler invaded Hell, I would at least make a favourable reference to the Devil in the House of Commons."
As a communicator he was unique. I remember a Belgian lady at a Churchill conference, gripping Lady Soames's arm to tell her what those speeches meant to Belgians gathered around surreptitious radios, listening to crackling broadcasts over the forbidden BBC. A former RAF pilot, briefly WSC's detective after the war, told me: "After one of those speeches, we wanted the Germans to come."
See more on Churchill in Richard's upcoming book “Winston Churchill, Myth and Reality”.