Ivan was also the first Russian ruler to invade Europe, and his Campaigns against the Livonian Confederation were initially very successful. In 1558, Russian soldiers occupied Dorpat and Narva, and laid siege to Reval, creating vital trade routes over the Baltic Sea. At the Battle of Ergema the Russians defeated the knights of the Livonian Order, fuelling Ivan's dreams of a Russian Empire.However, as Erik XIV of Sweden recaptured Reval, and the Poles joined forces with the Lithuannians, the war began to turn against Ivan. In 1571, an army of 120,000 Crimean Tatars crossed the River Ugra, crushed the Russian defences, and burned Moscow to the ground. As Ivan became increasingly paranoid and violent, he carried out a number of terrible massacres. It is thought that more than forty thousand were killed when the Russians sacked the town of Novgorod in 1570, and many were tortured and murdered in front of Ivan and his son. Ivan the Terrible describes the organisation and equipment of the tsar's army and the forces of his enemies, the Poles, Lithuanians, Tatars and Livonian Knights. The narrative examines all of Russia's military campaigns in Eastern Europe and Western Siberia during the period of 1533 to 1584. This is the first specialist study of Ivan the Terrible's military strategy to be published in English.