France used the right moment and occupied Alger in 1830. In 1831 Muhammad Ali of Egypt, who was the most powerful vassal of the Ottoman Empire, claimed independence. Ottoman forces were defeated in a number of battles, and Egyptians were ready to capture Constantinople, which forced the sultan Mahmud II to seek for Russian military aid. 10 000 Russian army corps landed on the Bosphorus shores in 1833 and helped to prevent the capture of Constantinople, thus the possible disappearance of the Ottoman Empire was prevented.