The ~ of a country or city that has been divided into two or more parts for some time is the joining of it together again.
...the ~ of East and West Beirut in 1991.
N-UNCOUNT: with supp
REUNIFICATION
Meaning of REUNIFICATION in English
Collins COBUILD. Толковый словарь английского языка для изучающих язык Коллинз COBUILD (международная база данных языков Бирмингемского университета) . 2012