Fleets are not confined to the ocean, but now sail over the land. … All the power of the British Navy has not been able to prevent Zeppelins from reaching England and attacking London, the very heart of the British Empire. Navies do not protect against aerial attack. … Heavier-than-air flying machines of the aeroplane type have crossed right over the heads of armies, of million of men, armed with the most modern weapons of destruction, and have raided places in the rear. Armies do not protect against aerial war.
Alexander Graham Bell in "Preparedness for Aerial Defense", Addresses Before the Eleventh Annual Convention of the Navy League of the United States, Washington, D.C., April 10-13, 1916 (1916), 70.