I find this ad both charming and a little weird.  There's something a little...romantic and even heroic, I guess...about what this man is trying to do, but I have to wonder what lady would take him up on this offer.  See for yourself:

Matrimonial. - A young unmarried cavalry officer, who intends to serve his country till "this cruel war is over," desires, should he be slain during the war, to leave an heir to his name and inheritance.  He therefore wishes to open correspondence with a view to matrimony with a patriotic young lady of intelligence, accomplishments, common sense, &c.  Address K, Nineteenth New York cavalry, Manassas Junction, Va.

The quote in here, "this cruel war is over," is the title of a song of the same name,