5The book describes and analyses the Swedish campaign in Muscovy of 1609-1610 and the Ingrian War between Sweden and Muscovy of 1610-1617, both of which took place during Russia's Time of Troubles. Faced with a serious threat from the Polish-Lithuanian Commonwealth, Moscow entered into an alliance with Sweden and ultimately offered the crown to young Gustavus Adolphus of Sweden. First, a Swedish expeditionary force under Jacob De la Gardie marched to Moscow in order to save Muscovy from a Polish-Lithuanian invasion army. However, De la Gardie and the Muscovites were defeated in the battle of Klushino. Later, Sweden conquered Novgorod. While the representatives of Gustavus Adolphus ruled Muscovy from Novgorod, a coup in Moscow led to the assumption of power of the first Tsar of the Romanov dynasty. Sweden accordingly went to war against Muscovy: the Ingrian War, in which Gustavus Adolphus laid siege to Pskov. The war ended with the 1617 Treaty of Stolbovo, in which Muscovy ceded key territories to Sweden while Sweden recognized the House of Romanov as rulers of Muscovy. For Sweden, the Treaty of Stolbovo has been described as the most successful peace ever negotiated with Muscovy or Russia. For Muscovy, the Treaty signified the ascension of the House of Romanov. For both countries, the war led to significant military reforms that, in time, would make both the Swedish and Muscovite military establishments forces to be reckoned with. For Gustavus Adolphus, who arrived in 1614 personally to take command of the Swedish war effort, the war in Muscovy proved a significant step on his path to become a successful commander in the subsequent Thirty Years' War. Michael Fredholm von Essen presents new research on two wars previously seldom described in English. Moreover, the book details the military systems of Sweden and Muscovy and explains the development of the Swedish Army before Gustavus Adolphus used it with great success in the Thirty Years' War.