Although officially the Swedish-Russian alliance was not ratified before July 1609, already in the early spring of 1609 Sweden gathered for this mission to the city of Vyborg (Finnish: Viipuri) in Finland (then part of Sweden) c. 5,000 soldiers, consisting mainly of Finns. A Swedish offensive heading towards Moscow – via Novgorod – began from Vyborg on 11 March 1609. The operation became known as De la Gardie campaign. It was a joint military campaign by the Tsardom of Russia and Sweden during the Polish-Russian War (1605-1618), a.k.a. Polish–Muscovite War or the "Dimitriads", lasting officially from April 1609 to 4 June 1610.