During many months the two emperors remained in a half-hostile condition, but the strain finally became too great. War was inevitable, and Napoleon set about preparing for the struggle. During the latter months of 1811 and the first of 1812 his attention was given almost entirely to the military and diplomatic preparations necessary before beginning the Russian campaign. By the 1st of May, 1812, he was ready to join his army, which he had centred at Dresden. Accompanied by Marie Louise he arrived at Dresden on the 16th of May, 1812, where he was greeted by the Emperor of Austria, the King of Prussia, and other sovereigns with whom he had formed alliances. The force Napoleon had brought to the field showed graphically the extension and the character of the France of 1812. The “army of twenty nations,” the Russians called the host which was preparing to meet them, and the expression was just, for in the ranks there were Spaniards, Neapolitans, Piedmontese, Slavs, Kroats, Bavarians, Dutchmen, Poles, Romans, and a dozen other nationalities, side by side with Frenchmen. Indeed, nearly one-half the force was said to be foreign. The Grand Army, as the active body was called, numbered, to quote the popular figures, six hundred and seventy-eight thousand men. It is sure that this is an exaggerated number, though certainly over half a million men entered Russia. With reserves, the whole force numbered one million one hundred thousand. The necessity for so large a body of reserves is explained by the length of the line of communication Napoleon had to keep. From the Nieman to Paris the way must be open, supply stations guarded, fortified towns equipped. It took nearly as many men to insure the rear of the Grand Army as it did to make up the army itself. [Illustration: PORTRAIT OF THE KING OF ROME. Painting by Lawrence. Collection of the Duc de Bassano. This portrait of Napoleon II. is an exquisite work of art, a bright and fresh color-harmony. Lawrence must have executed this portrait while travelling in Europe, whither he was sent by his sovereign George IV., and paid twenty-five thousand francs a year, to paint for the great Windsor gallery the portraits of all the heroes “_du grand hasard de Waterloo_.”—A. D.] With this imposing force at his command, Napoleon believed that he could compel Alexander to support the continental blockade, for come what might that system must succeed. For it the reigning house had been driven from Portugal, the Pope despoiled and imprisoned, Louis gone into exile, Bernadotte driven into a new alliance. For it the Grand Army was led into Russia. It had become, as its inventor proclaimed, _the fundamental law of the empire_.