You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Szlachta

Context:
Around the 14th century, there was little difference between knights and the szlachta in Poland. Members of the szlachta had the personal obligation to defend the country (pospolite ruszenie), thereby becoming the kingdom's most privileged social class. Inclusion in the class was almost exclusively based on inheritance.

Question:
What was a personal obligation of the szlachtas?

defend the country