On Trump’s pick for Vatican envoy, can a firebrand become a firebreak?

ROME – Famously, von Clausewitz defined war as “the continuation of politics by other means.” To hear some people tell it, President-elect Donald Trump has an analogous, if inverted, understanding of diplomacy as the continuation of war by other means, as exemplified by his Dec. 20 pick for U.S. Ambassador to the Vatican.

Brian Burch, president of the right-wing advocacy group CatholicVote and Trump’s choice for the job, has a reputation as a “pope critic,” leading skeptics of the nomination...