PAUL VI (Giovanni Battista Montini, 1897–1978), was pope of the Roman Catholic Church during most of the Second Vatican Council and the years immediately after it. Born to influential and prosperous parents in Concesio, near Brescia, Italy, the sickly young Giovanni was nurtured in an encompassing church environment and groomed for leadership beginning with his seminary career. By the time he was ordained in 1920 he had already begun making friends and adopting styles that were to be conducive to a diplomatic career in the church.

Pius XII wanted to name Montini a cardinal in 1953, but he declined this honor until 1958, when John XXIII endowed him with the title. Pius had earlier appointed the scholarly, diplomatic-minded cleric archbishop of Milan, a key post. Yet it was his years in the Vatican Secretariat of State, to which he had been related through various positions for three decades, that best...