Nine years later, in 1156, Prince Yuri Dolgoruki ordered the building of a wooden wall, which had to be redone many times, to go around the growing city. After the attack of 1237–1238, when the Mongols burned the city to the ground and killed its people living there, Moscow grew back and became the capital of the Vladimir-Suzdal principality (an amount of land ruled by a prince) in 1327. Its good place on the start of the Volga River helped the city to grow slowly bigger and bigger. Moscow turned into a peaceful and rich principality, known as the Grand Duchy of Moscow, for many years and a large number of people from across Russia moved to live there.