reunification

noun

1. (countable, uncountable)The unification of something that was previously divided; used especially of a country.

   “Many of Spenser's readers today find the cleavings and reunifications of Redcrosse and Una presenting a psychodrama of mental fragmentation […]”

   “With the collapse of the Wall and the reunification of Germany, the divided stations and railway lines of Berlin were 'reunited' too. The last 'ghost station' was reopened to all passengers in 1992, and the very term - "ghost station" - had come to denote any disused platform remaining from the divide.”