This study aims to explain whether the driving forces behind the development and acquisition of weapons systems to the Navy can get it´s explanation by theories of rational actors, or if there are other underlying factors. During the 1970s the Navy stood without any modern anti-ship-missile while the rest of the world entered into the missile age and developed anti-ship missiles. Even though Sweden was a pioneer in this branch until they stopped the development of anti-ship missiles in 1968. This case study is based on the acquisition of anti-ship missile RBS 15 and analyzed by Graham Allison’s political science model of the rational actor. The analysis is made from two different perspectives, where the first one is the Navy's perspective and looking for the answer how the acquisition had occurred on their rational choice. The second perspective is the government's perspective and this is compared and discussed on the basis of the historical events. This is to give answers to the differences identified between these two perspectives.   The result of the study is that the Navy's action rests on and can be explained by the model of the rational actor. This is because the navy during the whole period were seeking for a solution that meet the threats by the assigned tasks and objectives with the least impact. However, the author cannot find the explanation for the government's actions based on the model of the rational actor and its explanatory power may be found by other models.