Why did the Baltic-speaking area become smaller over time?

The Baltic-speaking area has significantly diminished over time due to the assimilation and displacement of Baltic tribes by neighboring groups, particularly Slavs and Germans.123

Starting from the middle of the 1st millennium CE, the vast eastern Baltic territory began to shrink as Slavic peoples migrated from the south. These eastern Baltic tribes were gradually assimilated by the Slavs, a process that was largely complete by the 14th century.2

Additionally, the western Baltic region faced pressures from the Teutonic Order and the Order of the Brothers of the Sword during the 13th century. These groups conquered Baltic lands, forcibly converting the population to Christianity and establishing a social order that marginalized indigenous speakers. Over the following centuries, various Baltic languages—such as Old Prussian, Yotvingian, Curonian, Selonian, and Semigallian—became extinct as their speakers were assimilated into Lithuanian, Latvian, German, or Slavic populations.143