After an absence of four months, we returned here on the 24th instant, and found the Turks in the highest spirits. The Emperor has declared against them: but this was a proceeding they had been prepared for; and, far from his arms having as yet been attended with any decisive success, he tarnished them in the onset, by beginning the war in a pusillanimous style, not at all expected from so powerful an enemy. We had scarce left this country, before advice was received of a treacherous attempt to take Belgrade; but the slovenly manner in which this enterprise was conducted, gave the Emperor an opportunity of denying his being privy to it. It proved unsuccessful; and, as the Baron De Herbert, the Imperial Minister, had changed his threats into negociations for settling a peace between Turkey and Russia, the Porte, unwilling to provoke the Emperor to hostilities, and in hopes that this failure would discourage him from pursuing his designs against a people who were so much better prepared than he expected, very politically seemed to admit the Internuncio's excuses for this breach of faith. It seems, that an officer who had passed through Belgrade, reported at Vienna, that the fortifications were in a most ruinous state, and that none of the cannon were fit for service. On this fallacious information, orders were hastily sent to Generals Mitrowski and Alvinzy, to pass the Save, with a detachment of troops, who were to be supported by Generals De Gomingen and Klebeck, and to make an immediate attempt on this important fortress; but the latter Generals not arriving at the appointed time, and the fortifications appearing in a very different state from that in which they had been represented, Mitrowski and Alvinzy were obliged to retreat, and to repass the Save. Notwithstanding the Internuncio's disavowal of the Emperor's knowledge of this attempt, accounts were soon received, that Generals Mitrowski and De Gomingen were ordered to Vienna, to answer for their failure; and, on the 8th of February, Baron De Herbert delivered a formal declaration of war. After the journey to Cherson, the unremitting armaments which immediately followed, and, to crown the whole, the treacherous attempt upon Belgrade, the Imperial Manifesto, to the surprise of every body, begins in the following manner.-- "All Europe have been witness to the good faith with which the Court of his Imperial Majesty has, for many years, cultivated peace with the Ottoman Empire; the sincere dispositions it has manifested, on every occasion, to preserve their good neighbourhood; its disinterested and indefatigable endeavours to avoid any interruption of their mutual harmony, and its readiness to lend every office of mediation, to prevent any rupture between the Porte and the neighbouring Courts. These pacific intentions, &c. &c."