But this drastically changed when Emperor Theodosius I issued the Edict of Thessalonica in 380 A.D., making Catholic Christianity the religion of the Roman Empire. This marriage of church and state swung open the doors for Christian participation in the military of the Roman Empire. And sadly, Christians have been fighting for empires ever since.
But modern era popes have been leading the Catholic Church step-by-step back to its nonviolent beginnings; back to its peace-centered Gospel roots.
From St. Pope John XXIII to Pope Francis, popes have strongly condemned violence, war and all forms of bloodshed.
The Holy See's former nuncio (ambassador) to the United Nations, Archbishop Celestino Migliore, said the Vatican attitude for centuries was: "War is inevitable, so let's put some strict conditions to limit its effects [the just-war theory]. In these last decades we have adopted a different perspective and we say peace is possible, so let's work tirelessly for peaceful solutions."
The Conference of Major Superiors of Men (CMSM) – in leadership support of 17,000 religious priests and brothers in the U.S. – on Aug. 3, at their national assembly overwhelmingly passed a resolution titled "Gospel Nonviolence: The Way of the Church."
This resolution is another major step towards recovering the Catholic Church's nonviolent foundation. It is a cooperative response to Pope Francis' 2017 World Day of Peace Message which affirmed that "true followers of Jesus embrace his teaching about nonviolence" and "make active nonviolence our way of life."