In one of his speeches, Otto Von Bismarck said:

Not through speeches ... are the great questions decided ... but (instead) by iron and blood?

What does he mean by this?

Otto Von Bismarck is remembered as the Iron Chancellor. He was an outstanding diplomat who did much for the unification and economy of the German nation. But while he did favor diplomacy he also resorted to war on some occasions to unite the Germans and to expand the country's borders. So the first half of the sentence refers to diplomacy, and the other half refers to war since iron is for weapons and blood is for lives that are lost for new territory.