The June 2023 edition of the IRMO Brief, authored by Gordan Akrap, deals with the Finnish accession to the North Atlantic Alliance, which took place on 4th April this year. With Finland joining NATO, the Alliance at this moment has 31 members. After Russia launched its invasion of Ukraine in February last yeast, Finland decided to break its long-lived policy of neutrality and become a member of NATO. Thus, instead of weakening the Alliance, with Finland in NATO, Russia is now faced with the doubled length of its border with NATO member states. Finland will undoubtedly greatly contribute to the Alliance’s strength as its armed forces are very well trained, equipped, organized, structured and effective. The author also analyses how Sweden could further strengthen the Alliance and explores obstacles lying ahead of yet another Nordic country joining NATO.