In 1655 Sweden was the premier military power in northern Europe. When Sweden invaded Poland, in June 1655, it went to war with an army which reflected not only the state's military and cultural strengths but also its fiscal weaknesses. During 1655 the Swedes won great successes in Poland and captured most of the country. But a series of military decisions transformed the Swedish army from a concentrated, combined-arms force into a mobile but widely dispersed force. Fiscal necessities also drove acts of violence which quickly angered the Polish populace. This sparked a religiously fueled partisan insurgency against Swedish occupation. This insurgency created a stalemate in the war. This stalemate allowed foreign powers, including Austria, Muscovy and Denmark, to intervene in the Swedish-Polish war to advance their own interests. This dissertation examines the dangers of a strong military power trying to occupy a culturally diverse and exotic state without adequate resources to obtain all of the military and political goals of the war.