The European powers had reconciled after the tumultuous Napoleonic wars at the Congress of Vienna in 1815. A principle of “Balance of Powers” was implemented, and “Concert of Europe” was embraced by all European monarchs. Every territorial expansion and annexation were to be agreed upon by the five signatories (Britain, Russia, Austria, Prussia, and France) to the body of treaties. Though no representative of the Ottoman Sultan attended the Congress, it was understood that no annexation or invasion of the Ottoman lands was to be undertaken by any European power without the consent of other co-signatories. It was a resolution for peace after a quarter century of French revolutionary havoc.
Then the Greek revolt happened, a Russian patronized and funded insurrection. However, the Ottoman doubled down on the rebels and defeated them savagely, all the while committing a series of vicious atrocities against the Greek people.
Russia beseeched the European powers to join forces and help the Greeks, but the rest of the European powers were justified in their fear of Russian intentions. After all, it was the intent of Empress Catherine II (Empress of Russia 1762 – 1796) to recreate the Byzantine Empire, via her ambitious Greek plan, establishing a Greek state of Orthodox Christians, occupying the same territorial and political space as that of the old Byzantine Empire. A country under the implicit Russian control, politically and spiritually.
The European governments ignored the Russian calls, but European volunteers, inspired by religious and romantic revolutionary spirit flocked to Greece to join forces with the rebels. With the Ottoman control over the Greek dominion struggling, the Ottoman Sultan, Mahmud II, asked for help from his powerful governor of Egypt, Muhammad Ali Pasha. On hopes of advancing his own benefits, the Pasha of Egypt sent his eldest son, Ibrahim, an inspired military commander, disciplined and vicious in his own right. The Egyptian forces, under Ibrahim, quashed the Greek rebellion completely, committing farther atrocities in the wake of their suppression, killing thousands, burning villages and intending to ship thousands of Greeks to Egypt as slaves.
Compelled by public uproar and imminent Russian interference, Britain and France joined forces with Russia and sent a vast naval force. Buoyed by anti-Ottoman and philhellene passion, the British Admiral of the joint fleet, Admiral Codrington, disregarded the instructions for imposing a resolution by peaceful means and instead destroyed the entire Turkish and Egyptian fleets in Navarino, October 1827.
Imperial Russia had effectively dealt a devastating blow to its southern neighbor and was on the road to fulfilling its ambition of establishing the Greek state.
However, the Russians under the new crowned Emperor, Nicholas I, were too hasty to collect the spoils of war, disregarding the fears of the European powers who had just been on their side.
The Ottomans responded to the Russian participation in the naval onslaught at Navarino, by closing the Dardanelles to the Russian ships.
The Russian responded by invading the fatigued, demoralized Ottoman Empire in 1828, and was on the verge of conquering Constantinople, the long-vaunted holy city, and the capital of the Ottoman state.
Summer of 1829 would have been the real end of the Ottoman Empire. Why it continued to exist for almost another century is the result of the complicated geopolitical and diplomatic nature of continental Europe at that moment. A consequence of the vicious quarter century of revolutionary and Napoleonic wars and the tightly enforced Concert of Europe that had resulted from the Congress of Vienna, 1815.
The Austrian Empire refused to join the Russian side and fearing an Anglo-French intervention; the Russian forces pulled back. However, the Russians didn’t leave empty-handed. It received Ottoman recognition of all Black sea-lands annexed by Russia after the previous war (1768 – 1774), Russian protectorate over the Danuban principalities (modern Romania), and autonomy for Serbia, in addition to an immense influence over the Ottoman internal affairs.
Western European sentiment soured toward Imperial Russia and fear of an expansionist policy of the new emperor (like that of his grandmother, Catherine II) was in the air. British conspiracy theories of Imperial Russia sweeping through the near-east and threatening British India were prevalent at that time.