In his times he was one of the most powerful people in the Commonwealth, often described as a "de facto" ruler of the entire Grand Duchy of Lithuania. During the "Deluge", the Swedish invasion of Poland-Lithuania during the Second Northern War, he sided with the Swedish king signing the Treaty of Kėdainiai and the Union of Kėdainiai. This move however antagonised him with most of other nobles, including members of his own family. His forces were eventually defeated in battle and he himself died in a besieged castle at Tykocin.