In his thoughtful essay on Pius XII (“Humanity’s Conscience?” February 24), John Connelly writes that I belong to the group of historians who allege that Pacelli, through his silence, aided Hitler and the Nazis. In fact, my thesis, and the significance of my book’s title, Hitler’s Pope, has a different impetus. My main contention is that as secretary of state under Pius XI, Pacelli negotiated in 1933 a treaty known as the Reichskonkordat, which unintentionally aided Hitler’s project at an early stage before the Nazi police state was established.