From the 17th to the 19th century sailing vessels held their own. Then, in a comparatively few years, there was a revolutionary change in naval architecture, precipitated by the introduction of steam, the screw propeller, shell guns, and the use of iron and steel in building. Colonial and commercial expansion, imperialism rampant, and the subsequent need for defense and commercial protection, speeded up a race, further enhanced by the armament industry. Publicity spread the nightmare of invasion and war on trade. England was surrounded by enemies, -- France, Spain, South Africa, Russia, Turkey -- and the Americas were none too friendly. The century old problem of expanding the fleet or dividing it to protect various fronts; the howls of unpreparedness, all seem echoes of today. Then with 1905, the German Navy began to be a menaoe, and the introduction of dreadnaughts gave her a chance to start almost even with Britain -- and a new phase was opened. Historical -- carefully documented.