This thesis discusses the topic of Tokugawa shogunate defense policy at the turn of 18th and 19th century. This period is defined by the arrival of Adam Laxman's expedition to Japan in 1791 and the year of 1825, which is defined by the adoption of the Edict to Repel Foreign Vessels (ikokusen učiharai rei 異国船打ち払い令) and the publication of the key work of the Confucian scholar Aizawa Seishisai (会沢正志斎, 1782-1863), the New Thesis (Shinron 新論). The aim of the thesis is to analyze in detail the steps of the shogunate government defense policy based on the analysis of specific historical events, and to answer the research questions. Given the topic of the thesis, I consider it necessary to put Japanese defense policy in a broader context. The first two chapters are devoted to the time period that chronologically precedes the period defined in the thesis topic and they analyze Japanese defense policy and foreign relations during the 17th century. Chapter 1 focuses on contacts in the southeast and the roots of Christian missions in Japan. Chapter 2 discusses the shogunate's contacts on the northern border. The following part of the thesis focuses on the intellectual tradition and the spread of the Dutch learning in Japan. The main content of the fourth and fifth chapter is the analysis of specific events at the turn...