The attitude of Czech King Ferdinand I of Habsburg towards the ongoing First Austro-Turkish War (1525-1541) is presented on the basis of an analysis of documents of a private nature, written either by the monarch himself, or by those close to him. Correspondence between Ferdinand I, Emperor Charles V and Marie of Hungary, along with letters from Anna Jagellon, reflect the perceptions of danger and the ensuing models of behaviour inspired by various experiences, positions and interests.