On September 3, 1971, the parties made a breakthrough in the negotiations. This roundtable focused on preparatory work based on practical provisions that would improve conditions in West Berlin and eliminate irritable barriers. The four-power agreement on Berlin stated: „The Soviet guarantee of unfettered and preferential civilian traffic between the western sectors of Berlin and the Federal Republic of Germany is a central fact of the agreement and a substantial improvement. Under the new agreement, Bulgaria was divided into two parts along the Balkan mountain: the north, which was declared an autonomous principality paying tribute to Turkey; and the south (East Rumélie) – it remained under Turkish rule over the conditions of administrative autonomy. Macedonia, which was part of Bulgaria under the Treaty of San Stefano, was also transferred to Turkey. These treaties were part of a revolutionary series of international agreements, considered by some to form the division of Europe during the Cold War, while others saw this as the beginning of the process that led to the end of the Cold War. Mr. E. Sarotte wrote in 2001 that „… Despite all the fears, both sides have managed to make a lot of good deals through the dialogue of relaxation.  The Nixon administration considered the resolution of concrete issues that divide Europe to be a priority for a successful détente policy – the easing of hostility or tensions between countries through negotiation rather than confrontation. One of these topics focused on 20 years of disagreement over the ideal solution for Berlin.
The ideal solution for the Berlin question was reunification, but in the face of tensions between all those responsible, it was simply not possible. The Treaty of Berlin (formally the treaty between Austria-Hungary, France, Germany, the United Kingdom and Ireland, Italy, Russia and the Ottoman Empire for the colonization of business in the East) was signed on 13 July 1878.   After Russia`s victory over the Ottoman Empire in the Russo-Turkish War of 1877-1878, the great powers restructured the map of the Balkan region. They reversed some of the extreme profits that Russia claimed in the previous San Stefano contract, but the Ottomans lost their main stakes in Europe. It was one of three major peace agreements after the Vienna Congress in 1815. It was the last act of the Berlin Congress (June 13 – July 13, 1878) and included Great Britain and Ireland, Austria-Hungary, France, Germany, Italy, Russia and the Ottoman Empire.