Final answer:
Greece gained independence from the Ottoman Empire in 1830 after a decade of struggle, including the intervention of European powers.
Step-by-step explanation:
Independence of Greece from the Ottoman Empire
The country that gained independence from the Ottomans in 1830 was Greece. The struggle for independence began with the Greek War of Independence (also known as the Greek Revolution) in 1821. After reports of Ottoman atrocities against the Greeks reached Europe, there was an international outcry, leading to the intervention of Britain, France, and Russia. The combined effort of these powers led to a decisive naval battle in 1827, where the Ottoman fleet was sunk. With continued support from these countries, and Russia declaring war on the Ottoman Empire, Greece was finally recognized as an independent nation in 1830 following the signing of the Treaty of Constantinople.
In the broader context, the Ottoman Empire was experiencing a period of decline, with nationalism stirring revolutions across its territories. Inspired by the success of the Greeks, other Balkan nations such as Serbia, Romania, and Bulgaria achieved independence in the following decades. However, the immediate nation to gain independence after the Greek War of Independence was Greece itself, marking the beginning of the Empire's disintegration and the rise of nationalism within its former territories.