Read this: The Ottoman Navy vastly contributed to the expansion of the Empire's territories on the European continent. It initiated the conquest of North Africa, with the addition of Algeria and Egypt to the Ottoman Empire in 1517. Starting with the loss of Greece in 1821 and Algeria in 1830, Ottoman naval power and control over the Empire's distant overseas territories began to decline. Sultan Abdülaziz (reigned 1861–1876) attempted to reestablish a strong Ottoman navy, building the largest fleet after those of Britain and France. The shipyard at Barrow, England, built its first submarine in 1886 for the Ottoman Empire.
Now answer this question, if there is an answer (If it cannot be answered, return "unanswerable"): In what year did the Ottoman empire lose Greece?
1821