The Russo-Swedish War of 1590–1595 was instigated by Boris Godunov in the hope of gaining the territory of the Duchy of Estonia along the Gulf of Finland belonging to Sweden since the previous Livonian War. As soon as the Truce of Plussa expired early in 1590, a large Russian army led by Godunov and his sickly brother-in-law, Fyodor I of Russia, marched from Moscow towards Novgorod. On 18 January they crossed the Narva River and laid siege to the Swedish castle of Narva, commanded by Arvid Stålarm. Another important fortress, Jama (Jamburg), fell to Russian forces within two weeks. Simultaneously, the Russians ravaged Estonia as far as Reval (Tallinn) and Finland as far as Helsingfors (Helsinki). Sweden, in May 1595, agreed to sign the Treaty of Teusina (Tyavzino, Tyavzin, Täyssinä). It restored to Russia all territory ceded in the Truce of Plussa of 1583 to Sweden except for Narva. Russia had to renounce all claims on Estonia, including Narva, and Sweden's sovereignty over Estonia from 1561 was confirmed.