This was followed, on May 21, 1853, by the departure of Prince Menschikoff from Constantinople, with the threat that “he had come in his great coat, but would return in his uniform.” Russia then crossed the Pruth on July 2nd, and occupied the Danubian Principalities as a preliminary to her demands. On the same day of the Russian invasion the representatives of the Great Powers assembled at Vienna. This Congress drew up what is known as the “Vienna Note.” Russia acceded to the terms contained in the Note, but the Porte refused, and offered certain amendments. The Powers after a time accepted them, and forwarded them to Russia, who, however, rejected them.[67] The Conference then dissolved. In October, 1853, the Porte declared war on Russia; and the destruction of the Turkish fleet at Sinope sealed the Russian acquiescence to the declaration. England and France allied themselves with Turkey against Russia, and declared war on March 28, 1854. The siege of Sebastopol lasted for nearly a year, and its fall was followed by the Congress of Paris.[68] The plenipotentiaries of France, England, Russia, Turkey, Sardinia, Austria, and at last Prussia, assembled at Paris (February, 1856), and the “Treaty of Paris” was signed, by which the following matters were settled:— 1. The Great Powers “declare the Sublime Porte admitted to participate in the advantages of the public law and system (concert) of Europe. Their Majesties engage, each on his part, to respect the independence and the territorial integrity of the Ottoman Empire; guarantee in common the strict observance of that engagement; and will, in consequence, consider any act tending to its violation, as a question of general interest” (Art. VII.). 2. “The Black Sea is neutralized; its waters and its ports thrown open to the mercantile marine of every nation, are formally and in perpetuity interdicted to the flag of war, either of the Powers possessing its coasts, or of any other Power” (Art. XI.), and, “The Black Sea being neutralized according to the terms of Article XI., the maintenance or establishment upon its coast of military maritime arsenals becomes alike unnecessary and purposeless; in consequence, His Majesty the Emperor of all the Russias, and His Imperial Majesty the Sultan, engage not to establish or to maintain upon that coast any military maritime arsenal” (Art. XIII.). The docks and fortifications at Sebastopol were destroyed by the Western Powers; but it was allowed that Russia and the Porte should keep up “the number of light vessels necessary for the service of the coast” (Art. XIV.), and merchant ships of all kinds were allowed freely to enter it.