Pacem in Terris was a papal encyclical

Encyclical

An encyclical was originally a circular letter sent to all the churches of a particular area in the ancient Catholic Church. At that time, the word could be used for a letter sent out by any bishop...

 issued by Pope John XXIII

Pope John XXIII

-Papal election:Following the death of Pope Pius XII in 1958, Roncalli was elected Pope, to his great surprise. He had even arrived in the Vatican with a return train ticket to Venice. Many had considered Giovanni Battista Montini, Archbishop of Milan, a possible candidate, but, although archbishop...

 on 11 April 1963. It was the last encyclical drafted by John XXIII, who died from cancer

Cancer

Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

 two months after its completion .

Pacem in terris was the first encyclical that the Pope did not address to the Catholic

Catholic

The word catholic comes from the Greek phrase , meaning "on the whole," "according to the whole" or "in general", and is a combination of the Greek words meaning "about" and meaning "whole"...

 faithful only, but also to "all men of good will".

In this work, John XXIII reacted to the then political situation in the middle of the Cold War

Cold War

The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...

.