Peter Maurin, born in France, was the spiritual mentor of Dorothy Day, and co-founder with her of the Catholic Worker Movement. The Catholic Worker Movement has embraced Christian pacifism from its earliest days.
Maurin was not a prolific writer, preferring to share his ideas in person, but he did write a book called Catholic Radicalism: Phrased Essays for the Green Revolution, which is made up of a series of what came to be known as "easy essays." On this page, we link to the book on the Internet Archive so you can visit it and read some of the easy essays that deal with peace and war.
Click the image below to read all the easy essays. Some of those dealing with peace and war are on pages 119-120, 122-123, 142-144, 156-157.
Photo of Dorothy Day and Perer Maurin. Source: http://thefanzine.com/revisiting-the-catholic-worker-movement-dorothy-day-and-anarcho-socialist-christianity/
Hear the only known recording of Peter Maurin