II. About the women who married again when their husbands were taken prisoners.
As then you say that through the disasters of war and through the grievous inroads of the enemy families have in certain cases been so broken up that the husbands have been carried off into captivity and their wives remain forsaken, and these latter thinking their own husbands either dead or never likely to be freed from their masters, have contracted another marriage under stress of loneliness, and as, now that the state of things has im proved through the Lord's help, some of those who were thought to have perished have returned, you seem, dear brother, naturally to be in doubt what ought to be settled by us about women thus joined to other husbands. But because we know it is written that “a woman is joined to a man by God,” and again, we are aware of the precept that “what God has joined, man may not put asunder,” we are bound to hold that the compact of the lawful marriage must be renewed, and after the removal of the evils inflicted by the enemy, what each lawfully had must be restored to him; and we must take every pains that each should recover what is his own.
Source: Letters (New Advent)