After the definitive peace, deferred by the hundred days, but finally forced upon France on the field of Waterloo, the Prussian Government continued to foster the school of war which it had founded in the period of humiliation. Prussian officers trained in that school tried to learn the lessons of the long period of war which they had passed through. What they discovered was that war between nations, as distinct from war between dynasties or royal houses, was a struggle for existence in which each adversary risked everything and in which success was to be expected only from the complete prostration of the enemy. In the long run, they said to themselves, the only defence consists in striking your adversary to the ground. That being the case, a nation must go into war, if war should become inevitable, with the maximum force which it can possibly produce, represented by its whole manhood of military age, thoroughly trained, organised, and equipped. The Prussian Government adhered to these ideas, to which full effect was given in 1866, when the Prussian army, reorganised in 1860, crushed in ten days the army of Austria, and in 1870 when, in a month from the first shot fired, it defeated one half of the French army at Gravelotte and captured the other half at Sedan. These events proved to all continental nations the necessity of adopting the system of the nation in arms and giving to their whole male population, up to the limits of possibility, the training and the organisation necessary for success in war. The principle that war is a struggle for existence, and that the only effective defence consists in the destruction of the adversary's force, received during the age of Napoleon an even more absolute demonstration at sea than was possible on land. Great Britain, whether she would or no, was drawn into the European conflict. The neglect of the army and of the art of war into which, during the eighteenth century, her Governments had for the most part fallen, made it impracticable for her to take the decisive part which she had played in the days of William III. and of Marlborough in the struggle against the French army; her contributions to the land war were for the most part misdirected and futile. Her expeditions to Dunkirk, to Holland, and to Hanover embarrassed rather than materially assisted the cause of her allies. But her navy, favourably handicapped by the breakdown, due to the Revolution, of the French navy, eventually produced in the person of Nelson a leader who, like Napoleon, had made it the business of his life to understand the art of war. His victories, like Napoleon's, were decisive, and when he fell at Trafalgar the navies of continental Europe, which one after another had been pressed into the service of France, had all been destroyed.