Pope Francis on his way ...

Apostolic visit to Chile and Peru. 

As he boarded the plane for Chile on Monday, Pope Francis spoke of his fears in the face of threats of nuclear war. Talking to journalists on the papal plane, he also commented on the image of a young Japanese boy carrying the body of his baby brother on his back as he waited in line at a crematorium in the city of Nagasaki. - Vatican News

"Presumption is the crime of idolatry." - Today's first reading, Samuel 15: 16-23 

No one ever listens to popes when they attempt to broker peace.  Paul VI was ignored when he cried, "No more war!" at the United Nations.  John Paul II was ignored in his many please for peace as well.  From the beginning of his Pontificate he worked for peace.  In his address to the United Nations in 1982 he made his plea for disarmament:

The teaching of the Catholic Church in this area has been clear and consistent. It has deplored the arms race, called nonetheless for mutual progressive and verifiable reduction of armaments as well as greater safeguards against possible misuse of these weapons. It has done so while urging that the independence, freedom and legitimate security of each and every nation be respected. 

I wish to reassure you that the constant concern and consistent efforts of the Catholic Church will not cease until there is a general verifiable disarmament, until the hearts of all are won over to those ethical choices which will guarantee a lasting peace.

[My Predecessor, Pius XII, as early as 1946, referred to "the might of new instruments of destruction" which "brought the problems of disarmament into the center of international discussions under completely new aspects" (Address to the College of Cardinals, December 24, 1946).] - Vatican

Perhaps prophetically, Pope Benedict XVI, when explaining the reason for his name choice said:

In taking this name, I wanted to evoke both the Patron Saint of Europe, who inspired a civilization of peace on the whole continent, and Pope Benedict XV .... planning to acquire them— agree to change their course by clear and firm decisions, and strive for a progressive and concerted nuclear disarmament. - Holy See

It's maybe good to remember that in 1916-1917 Europe rejected the Papal Peace Plan of P. Benedict XV.  Catholics and Protestants alike seemed insulted that a Pope would attempt to broker peace.