World War II marked a turning point in modern humanity. It was a turn in the international political scene where countries like the United States and the Soviet Union have taken the lead. Although these two superpowers emerged from the war as allies, they soon became opposing actors in a new global struggle in which two opposing blocs were formed - the West and the East. There was the creation of security alliances on both sides, NATO as a representative of the Western bloc and the Warsaw Pact as a representative of the Eastern bloc. Analogous to the collapse of the Soviet Union, the Warsaw Pact ceases to exist and NATO remains the strongest international military-security alliance. With the disappearance of the Soviet Union, the purpose and role of NATO became questionable. A transformation of the nature of NATO was necessary in order for the Alliance to adapt to new security challenges and threats. One of the features of modern NATO was the expansion of the Alliance to the east, ie the gradual inclusion of the countries of the former Eastern bloc in NATO. NATO enlargement has not bypassed the area of Southeast Europe and thus Croatia, for which joining NATO was one of the main foreign policy and security goals after independence and the Homeland War. With the accession of the Republic of Croatia to NATO, it was clear that the domestic armed forces would get the wind in their backs in terms of modernization and development of new capabilities. It is the latter factor that is the center of this thesis. The research problem of this paper refers to a vague overview of the capabilities achieved within the Croatian Armed Forces (CAF) that NATO seeks to develop in each of its member states. The aim of this research is to determine which capabilities, which the Republic of Croatia has agreed with the NATO Alliance, have been achieved within the CAF and to investigate the main forms of modernization that the domestic armed forces have achieved by joining the NATO Alliance. By analyzing domestic and foreign strategic documents and using scientific and professional literature, the paper concludes that some of the capabilities listed in Croatian strategic documents, some of which are prescribed by NATO to each member state, have been developed while some of these capabilities are still unrealized. It is evident from this thesis that Croatia's accession to NATO had a positive effect on the development and modernization of the CAF, but that some key capabilities were missing and that the real picture of developed CAF capabilities is not completely identical to the capabilities listed in strategic documents.