Following a series of conflicts between Poland and Sweden in 1600–11, 1617–18 and 1621–1625, all of which ended in a stalemate, Gustavus Adolphus invaded in 1626 to gain control over Livonia and relinquish Sigismund's claim to the Swedish crown. Sigismund, already in advanced age, continued his long-term ambition to seize Sweden, which gave Gustavus Adolphus a reasonable casus belli and justification for war. Though the Polish army achieved major victories in the previous battles against Sweden, particularly at Kircholm in 1605, the very end proved to be catastrophic.