Russification was the policy of enforcing Russian culture on the vast numbers of ethnic minorities that lived in the Russian Empire. It greatly affected the Poles, Lithuanians and the Ukranians. It was introduced after the assassination of Alexander II in 1881 and was the source of much resentment.
Russian was the official language and all others were suppressed. Poles were banned from speaking or learning their language in many places.
Russian Orthodoxy was promoted and Catholic monasteries were closed. Often, the Orthodox Church would take over former Catholic Churches.
Until 1891 Finland had its own parliament, laws and government. The majority of the population were satisfied with the arrangements and were supporters of the Tsar. The introduction of Russification resulted in widespread discontent. This led to the assassination of the Russian Governor General of Finland in 1904. Russification meant that a loyal part of the Empire had become an enemy of the Tsar.
During Nicholas II’s reign, the Black Hundreds was formed. This was an extreme nationalist movement that supported the Tsar and attacked groups who were seen as disloyal. They assassinated pro-democratic politicians and intimidated the workers in the towns. They also organised pogroms or attacks on Jews living within the Empire.