Both Sweden and Finland express a will for a deepened defence cooperation, but the problem is that such a cooperation haven’t been successful in the past. This paper aims to create an understanding about whether this defence cooperation have the requirements to succeed or if it faces a similar destiny as those which have failed in the past. This is conducted by examining how different strategic cultures, which covers the foreign-, security- and defense policy of an actor, can affect the cooperation and its possibility to succeed. The results show that Sweden is in a greater need of a deepened defence cooperation than Finland due to the increased strategic value of the Baltic Sea and its nearby regions, the increased threat this brings and the current state of the Armed forces which are developing towards territorial defence. This shows that Sweden are approaching Finland within these areas. While the biggest differences come through the historical experiences where cooperation have failed between the nations, at the cost of the suffering of Finland. This have led to a low Finnish trust towards cooperation and a mentality that they going to have to manage themselves.