The 16th and 17th centuries are regarded as something of a "dark age" in Greek history, with the prospect of overthrowing Ottoman rule appearing remote with only the Ionian islands remaining free of Turkish domination. Corfu withstood three major sieges in 1537, 1571 and 1716 all of which resulted in the repulsion of the Ottomans. However, in the 18th century, there arose through shipping a wealthy and dispersed Greek merchant class. These merchants came to dominate trade within the Ottoman Empire, establishing communities throughout the Mediterranean, the Balkans, and Western Europe. Though the Ottoman conquest had cut Greece off from significant European intellectual movements such as the Reformation and the Enlightenment, these ideas together with the ideals of the French Revolution and romantic nationalism began to penetrate the Greek world via the mercantile diaspora.[page needed] In the late 18th century, Rigas Feraios, the first revolutionary to envision an independent Greek state, published a series of documents relating to Greek independence, including but not limited to a national anthem and the first detailed map of Greece, in Vienna, and was murdered by Ottoman agents in 1798.[page needed]
Rigas Feraios was killed by Ottoman assassins in what year? 
1798