During the first transformation years of the 1990s, in spite of serious mistakes and avoidable decline, the introduction of a market and private economy progressed well in Central and Eastern Europe. It was strongly assisted by the European Union. As a result of political and economic consolidation and adjustment to the Union's requirements, transformation was essentially accomplished in most of the countries of the region over the decade beginning in the mid-1990s.

In a clear sign of political stability and security, virtually the entire region became part of the Western military alliance system, the North Atlantic Treaty Organization (NATO). As early as 1990, countries of the region were invited to the NATO Parliamentary Assembly as associate members. In the summer of 1997, Poland, Hungary, and the Czech Republic were invited to join NATO, which they did in 1999. Seven other countries from the region – Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia, and Slovenia – were invited to join at the November 2002 Prague summit. They joined in 2004. Article 5 of the NATO treaty, the collective security clause, guaranteed security to the members: “The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all.” Behind the Western military shield, integration into the West became easier.