Eastern Europe includes both historic Muslim communities as well as recently arrived Muslim refugees. Islam first came in conquering waves. Mongol invaders in the 13th century had adopted Islam following their conquests. Next came the conquest of Muslim Tatars. Finally, the Ottomans occupied most of Eastern Europe from the 14th to the 17th centuries.
After the decisive defeat of the Ottoman Turks in Vienna in 1683, Islam entered a two-century retreat, with waves of converted Europeans leaving with the retreating Turks.
Remaining Muslim communities have survived in Kosovo (95%), Albania (55%), Bosnia and Herzegovina (51%), North Macedonia (33%), Montenegro (20%), Bulgaria (11%), Latvia (7.7%), and Slovenia (3.8%). For the remainder of Eastern Europe – not counting Russia – the percentage of Muslims is mostly less than 1%.
The majority are Sunni, and are cultural, conservative, or even secular Muslims. Some 20% favor Sharia law and prefer to live in Muslim-majority communities.
Recently arrived Muslim refugees are generally not welcomed by Eastern Europeans. Initially they used Eastern Europe as the passage-way to Western Europe, but once Western Europe reached refugee saturation levels, European Union agencies asked Eastern European nations to accept national refugee quotas. Those requests were firmly rejected.