Deutsche Einheit May 1989 to October 1990
The opening of the Border in May 1989 Hungary led to fall of the Berlin Wall in November 1989. In reality it wasn’t just the Russians that had kept Germany divided after WWII in 1945, but the ‘Allies’ (mainly France, United Kingdom and USA) too wanted a divided Germany. Margaret Thatcher was then UK Prime Minister and was deeply opposed to the Reunification. This why the Germans even carefully called it Einheit (Unity) rather than Reunification.
On 1st July 1990, the Deutsche Mark replaced the East German mark as the official currency of East Germany.
The Volkskammer, the Parliament of East Germany, passed a resolution on 23rd August 1990 seeking the accession (Beitritt) of the German Democratic Republic to the Federal Republic of Germany as allowed by article 23 of the West German Basic Law, effective 3rd October 1990.