Step 1: Introduction to Poland's political condition.
During the nineteenth century, Poland did not exist as an independent nation-state. It had been partitioned and divided among powerful neighbouring empires such as Russia, Prussia and Austria. As a result, Polish people were politically suppressed and denied independent national identity. In this situation, language became an important instrument for preserving Polish nationalism.
Step 2: Language as a symbol of national identity.
The Polish language became a symbol of unity and resistance for the Polish people. Since political independence was lost, the people used their language to keep alive their culture, history and national memory. Speaking, reading and writing in Polish became an expression of loyalty to the nation. It reminded people that they belonged to one common community despite foreign rule.
Step 3: Russian attempt to suppress Polish language.
In the Russian-controlled part of Poland, the Russian rulers tried to impose the Russian language on the Polish people. After the Polish uprising of 1831, the use of Polish language was discouraged and Russian was made the language of administration and education. This was done to weaken Polish culture and assimilate the people into the Russian Empire.
Step 4: Role of Polish language in resistance.
The Polish people resisted this cultural domination by continuing to use their own language. Polish was used in churches, homes, literature and patriotic songs. The clergy also used Polish in religious instruction and worship. This made language a powerful tool of protest against foreign rule.
Step 5: Language and emotional nationalism.
Language helped create emotional unity among Polish people. It connected them to their past, their folklore, their literature and their collective suffering under foreign domination. Through poems, songs and writings in Polish, nationalist feelings spread among the masses. Thus, language became a cultural weapon in the struggle for national identity.
Step 6: Final conclusion.
Therefore, language played a very important role in the development of nationalism in Poland. It preserved Polish identity, resisted foreign domination and strengthened the desire for national independence. In the absence of political freedom, the Polish language became the foundation of national unity.
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\boxed{\text{Polish language became a symbol of national identity and resistance against foreign rule.}}
\]
Language played a key role in Polish nationalism because the Polish language preserved national identity, resisted Russian domination, united the people emotionally and kept alive the demand for independence.