Churchill made some major blunders. Google "gallipoli" for example.
Churchill saved England, but it was his spirit...his leadership...more than his strategic input.
As he said, "It was the nation and the race dwelling all round the globe that had the lion's heart. I had the luck to be called upon to give the roar."
Spirit yes, leadership, that too, but how? Through the English language, the strength of words.
I'm currently reading William Manchester's three volume bio of Churchill. Churchill was not in control of the Gallipoli which doomed it. Churchill favored a naval assault on Constantinople which probably would have succeeded. A preliminary naval assault up the coast had devastated weak Turkish defenses.
The Turks were making plans to evacuate the whole peninsula and move their military out of Constantinople. If the Allies would have acted in time, they probably could have taken Constantinople with little effort and knocked Turkey out of the war. That would have made more countries join the Allies and put enormous pressure on Germany.
However, the big men in charge of military affairs would not act promptly. They wasted many weeks vacillating before landing troops on the Gallipoli peninsula. By that time the Turks, with the help of the Germans, had built up their defences. The sea was still open to a concerted naval assault, but the Allied top military men refused to listen to Churchill.
So Churchill took most of the blame for the failure of Gallipoli, even though (1) he was not in charge and (2) his plan was poorly implemented.