This paper investigates the responsive behaviors of the King Gustav I of Sweden in connection with the two fortified border towns and adjacent areas of Kalmar in Småland and Viborg (today Vyborg) in the Karelian Isthmus from the outgoing letters sent by the king during three significant periods during his reign; 1527-1530 highlighting the Westrogothian rebellion, 1543-1544 with the climax of the Dacke War and 1555-1558 featuring the Russo-Swedish War and the delegations of Duchy of Småland and Finland to his eldest sons Eric and John. With the help of secondary literature we could pinpoint important courses of events that confirm the contexts of the letters.The results show that Gustav I was a highly demanding character who gave calls and advices to his subordinates regarding both military and civilian spheres. The nature of the letters can be categorized after four main themes: 1) Defensive counsels of the cities' fortifications, walls and castles 2) Military presence within the defenses’ facility and by the borders 3) The burgess' various complaints and problems 4) Trading rights and hindrance. The use of authority by law echoes throughout the letters, due of Gustav I:s position as King of Sweden.It is rather accepted today, that Gustav I was a product of his time with the teachings of Machiavelli spreading all over Europe. Traits as authoritarian rule and supervision over its subjects is a common feature in the letters during his lifetime, but also a hint of flexibility of the laws, giving his subjects exceptions during pressed and hard times.