NATO membership, which Sweden and Finland want to join, normally requires a long process. In order for NATO to accept new members, including Bosnia and Herzegovina, Georgia and Ukraine, various conditions must be fulfilled and legal processes must be completed.
NATO was founded by 12 countries in 1949, after the end of the Second World War. These countries were USA, UK, Canada, France, Italy, Netherlands, Norway, Portugal, Luxembourg, Iceland, Denmark and Belgium. In the 73 years that have passed, the number of members increased from 12 to 30 with 8 expansion waves.