During two years of diplomatic fencing the initiative had been Russian, the instigation French. For the war which followed no single cause can be assigned. Some blamed Napoleon, claiming that with his scheme of universal empire it was inevitable; Metternich said Russia had brought on war in an unpardonable manner. The Tilsit alliance was personal; the separation of the contracting parties inevitably weakened it. The affiliations of the Russian aristocracy with the Austrian; the smart of both under the Continental System, which rendered their agriculture unprofitable; England's stand under Castlereagh; the Oldenburg question--all these were cumulative in their effect. With Alexander, Poland and the Continental System were the real difficulties; the marriage question was only secondary. On January twelfth, 1812, the Czar with mournful and solemn mien declared his hands clean of blood-guiltiness and laid down his ultimatum. To the concentration of Russian troops Napoleon had replied by sending his own to Erfurt and Magdeburg. Alexander formally stated his readiness to take back his own move if the Emperor would withdraw the French soldiers; he would even accept Erfurt for Oldenburg, and permit Warsaw to be capital of a Saxon province. But he said not a word about the Continental System, being fully determined not to yield one jot, and for Napoleon this was the primary matter. Alexander's ultimatum by its clever form compelled his ally either to abandon the scheme of Western empire or to fight. Both parties to the Tilsit alliance understood that with European harbors shut to English trade, Great Britain must cease to support the Spanish insurrection, which in that case a few thousand troops could hold in check. Then the great scheme of revolutionary extension which had been inaugurated by the Convention and logically developed by Napoleon step by step in every war and treaty since Campo Formio would in a few short years be complete. But two real powers would thus remain in continental Europe--France and Russia. They could by united action crush British power both by land and by sea. To dash this brimming cup from his lips was for Napoleon an insupportable thought. With the hope, apparently, of securing from the Czar the last essential concession, he set his troops in motion toward the Vistula on the very day after his treaty with Prussia was signed.