In 1626, the Swedish Council of the Realm recommended that their king, Gustav II Adolph (1594–1632), should "negotiate with the enemy under the helmet" in order to force Poland into accepting Swedish demands. Although Gustav Adolph's reign is known especially for its wars and not for its diplomacy, this deliberate combination of military action and diplomatic approach illustrates the true status of diplomacy in Swedish foreign policy from 1617 to 1630. This book argues that diplomacy played a decisive role in the conduct of Swedish foreign policy during Gustav Adolph's reign. For the value of diplomacy in foreign policy greatly depends on how much emphasis a government puts on this means, it is reasonable to shed light on the establishment of diplomatic structures and how exactly they were employed. Did Gustav Adolph follow a clear-cut concept of diplomacy, or did the government react spontaneously with whatever diplomatic means they could procure at a given moment?