Лжедмитрий II
In 1609, the Vyborg Treaty was signed by Sweden and Tsardom of Russia as a package of military agreements that were supposed to be mutually beneficial to both countries. It was signed by King Charles IX of Sweden and Vasili IV (also known as Vasily Shuisky) of Russia in the Swedish city of Vyborg, located on the Karelian Isthmus close to Russian territory. The treaty came at an unstable period in Russian history known as the Time of Troubles, where the death of Tsar Feodor I in 1598 led to decades of civil war. In 1605, following the death of "de facto" ruler Boris Godunov, Vasily Shuisky came to power, triggering a conflict with a pretender to the Russian throne, False Dmitry II. Additionally, Russia began fighting the Polish–Muscovite War following invasion of the country by the Polish–Lithuanian Commonwealth the same year. Sweden themselves were fighting against the Poles in the Polish–Swedish War, and viewed their eastward expansion into Russian lands as a security threat. The terms of the Vyborg Treaty stipulated that Sweden would supply a corps of mercenaries to Shuisky to fight False Dmitry II and the Poles, in exchange for Swedish control of the nearby strategic Korela Fortress, as well as its town Kexholm and the respective county. Shuisky agreed to the terms, but was an unpopular ruler with little power. Shortly after signing the Vyborg Treaty, Russia's fortunes began to rise, and Shuisky was forced out of power in 1610. A coalition between Swedish general Jacob de la Gardie and Russian princes launched the De la Gardie Campaign, effectively defeating False Dmitry II.