In 1554 the Pechenga Monastery was raided by the Swedes. The governor of Novgorod Paletsky sent Nikita Kuzmin to Stockholm to ask for an explanation, but the Russian representative was imprisoned. In response Russia mounted an organized attack with up to 20,000 soldiers in March 1555. With its initially 1,000 men, Finland could not stand against the invading troops, but soon, reinforcements consisting of 3,700 infantrymen and 250 cavalrymen arrived from Sweden. The Finnish nobility had also been engaged in the war, contributing with its cavalry. The goal of the Swedish-Finnish troops was to conquer Oreshek, Korela and Koporye. The siege of Oreshek was badly planned by the Swedish side and failed since the Russians had destroyed the areas surrounding the town and the Swedish troops had insufficient supplies to be able to maintain the siege until the town surrendered. While admiral Johan Brigge besieged and bombarded Oreshek,  the Swedish diplomats tried to find support for their cause in Livonia, Poland-Lithuania and England. Early the following year, 1556, Russia made a new attack, this time with an army almost 20,000 men strong. The attack was aimed at the town of Viborg , and the Swedish troops were unlikely to withstand an army of that considerable size. However, after a few days of pillaging in the area around Viborg, the Russian forces left. The reason for this has not been made clear. Conceivable reasons might be bad discipline or a raging disease among the Russian soldiers. Perhaps it was never the aim to conquer Viborg, only to ravage the areas surrounding the town as a demonstration of power.
Question: How many years did these events span for?
Answer: 2