How can an intelligence chief change a war?

Did any intelligence chief significantly change the outcome of a battle?

Their larger effect usually came from managing information and political decisions across a war, with Canaris's influence on Chamberlain as one example.

An intelligence chief's effect cannot be reduced to a single battle. The important work is building teams, collecting information, shaping advice, and creating the situations in which leaders make decisions. Canaris offers a concrete example because his plots and warnings lodged themselves in Neville Chamberlain's thinking, including fears generated by the Dutch war scare. Intelligence influence is therefore better understood as a campaign across a war than as one sudden tactical victory.