On the 1st of September 1939, the Wehrmacht (German Army) invaded Poland, thus starting the deadliest conflict in History. The United Kingdom and France, Poland's allies, sent an ultimatum to Nazi Germany. On the 3rd of September, failing to receive an answer, they declared war on Germany.

At that time, a young Father Stephen McGill (to become 2nd Bishop of Paisley) was on the staff of Le Grand Seminaire at Bordeaux.

Reintroduced in May, the conscription called up to 1.5 million men by the end of the year. Though technically exempted, clergy (of any denomination) were encouraged to volunteer and provide religious, pastoral and moral support to soldiers. Fr Donald Bonnar, Fr Robert Barclay, Fr Vincent Grace and Fr Ferdinand Tritschler, all priests of the future Diocese of Paisley, became chaplain to the Forces.