The Ottoman Empire was an essential part of the balance of power in Europe. Its preservation had been for many years an object to the whole of Europe. While he acquitted the British admiral of all blame, he pointed out that, under the treaty of London, one of the stipulations was that the operation was not to lead to hostilities. When, therefore, the operation under the treaty did lead to hostilities, it certainly was an untoward event. It is difficult, however, to conceive how the Duke, who had negotiated the treaty with the Czar of Russia, could have supposed that, in the event of the Sultan not agreeing to the terms of mediation, the use of force against him could be avoided. However that might have been, the destruction of the Ottoman fleet at Navarino was of momentous importance. It cut off the communication between Ibrahim Pasha and Egypt. It restored to Greece command of the sea in the archipelago. It assured the supremacy of the Russian fleet in the Black Sea. This last was of enormous value to the Russians in the war which soon broke out with Turkey. It facilitated the capture of Varna, and enabled the Russian army to advance across the Balkans and to threaten Constantinople. Ibrahim Pasha, finding his position in the Morea untenable, entered into a convention with the British admiral under which he was permitted to withdraw the Egyptian army from Greece and embark it for Alexandria without molestation from the allied fleet. There remained in the Morea only the Turkish troops. They held most of the fortresses there. Later, a French army, under General Maison, was, by agreement with the allies, sent to the Morea. It soon cleared the whole country of the Turkish troops. Meanwhile, the Sultan at Constantinople, in spite of the destruction of his fleet at Navarino, still maintained an obstinate refusal to accede to the terms of the treaty of London. The ambassadors of England and France thereupon left the city. Differences then began to arise between the three allied Powers. The Emperor of Russia proposed to employ coercive measures against Turkey, and for this purpose to occupy Moldavia and Wallachia. England and France rejected the proposal. They wished to preserve the Ottoman Empire as well as to secure the independence of Greece. But the Greek question was only one of the complaints of Russia against Turkey. It had also grave reasons to complain that the treaty of Bucharest and the later treaty of Akermann of 1826, confirming and extending it, were disregarded by the Porte, which still occupied Moldavia, Wallachia, and Serbia by its armies. The Sultan, in a manifesto to his own people, had publicly announced that he had entered into the treaty of Akermann with the full intention of not being bound by its terms, and that he regarded Russia as his hereditary foe.