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:
Ottoman_Empire

Context:
The effective military and bureaucratic structures of the previous century came under strain during a protracted period of misrule by weak Sultans. The Ottomans gradually fell behind the Europeans in military technology as the innovation that fed the Empire's forceful expansion became stifled by growing religious and intellectual conservatism. But in spite of these difficulties, the Empire remained a major expansionist power until the Battle of Vienna in 1683, which marked the end of Ottoman expansion into Europe.

Question:
Poor rule by what class of people strained the empire?

Sultans