in 1991, a year after german reunification, east germany's deutscher fußball-verband der ddr, or football federation of the german democratic republic, was merged into west germany's dfb. east german sides were seeded and assigned to various levels within the west german league structure, which was itself modified to accommodate the influx of new clubs. to facilitate the union with the eastern league the bundesliga temporarily expanded to 20 clubs in the 1991–92 season and added the ddr-oberliga's top two sides, dynamo dresden and hansa rostock. the bundesliga returned to an 18 team slate in the following season with dresden managing to stick in the top league, while "rostock" was relegated. these two teams continued to make appearances in the bundesliga through the 1990s. the only other former east german sides to earn promotion to the bundesliga to date are fc energie cottbus and vfb leipzig, while a half dozen others of these clubs have played in 2. bundesliga.