A Long Petal of the Sea by Isabel Allende

In the late 1930s, civil war grips Spain. When General Franco and his Fascists succeed in overthrowing the government, hundreds of thousands are forced to flee in a treacherous journey over the mountains to the French border. Among them is Roser, a pregnant young widow, who finds her life intertwined with that of Victor Dalmau, an army doctor and the brother of her deceased love..