the Party of Democratic Socialism, was swept from power and replaced by a pro-reunification Alliance for Germany coalition led by the Christian Democratic Union (CDU), Chancellor Kohl's party. Both countries progressed rapidly towards reunification, while international diplomacy paved the way abroad. In July 1990, monetary union was achieved. A Treaty on the establishment of a unified Germany was agreed on in August 1990 and political reunification took place on 3 October 1990. Abandonment of the border The border fortifications were progressively torn down and eventually abandoned in the months following its opening. Dozens of new crossings were opened by February 1990, and the guards no longer carried weapons or made much effort to check travellers' passports. The guards' numbers were rapidly reduced; half were dismissed within five months of the opening. On 1 July 1990 the border was abandoned and the Grenztruppen were officially abolished; all but 2,000 of them were dismissed or transferred to other jobs. The Bundeswehr gave the remaining border guards and other ex-NVA soldiers the task of clearing the fortifications, which was completed only in 1994. The scale of the task was immense, involving both the clearing of the fortifications and the rebuilding of hundreds of roads and railway lines. A serious complication was the presence of mines along the border. Although the 1.4 million mines laid by the GDR were supposed to have been removed during the 1980s, it turned out that 34,000 were unaccounted for. A further 1,100 mines were found and removed following reunification at a cost of more than DM 250 million, in a programme that was not concluded until the end of 1995. The border clearers' task was aided unofficially by German civilians from both sides of the former border who scavenged the installations for fencing, wire and blocks of concrete to use in home improvements. Much of the fence was sold to a West German scrap-metal company. Environmental groups undertook a programme of re-greening the border, planting new trees and sowing grass seeds to fill in the clear-cut area along the line. Border area today Very little remains of the installations along the former inner German border. At least 30 public, private and municipal museums along the old line present displays of equipment and other artifacts relating to the border. Among the preserved sites are several dozen watchtowers, short stretches of the fence and associated installations (some of which have