Sweden joins NATO: Should Ukraine be next, and why are countries Russian to join?

In April, Finland became the latest member of the military alliance comprised of 29 European nations, Canada and the United States. Finland's accession roughly doubled NATO's border with Russia.

After stalling the process of Sweden joining NATO due to Turkey's concerns about the country harboring PKK members, President Erdoğan has given the green light for the Northern European country's accession to the military alliance. Speculations as to why the Turkish president changed course on such short notice are manifold. The most plausible reasons i…