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:
Mieszko I of Poland (c. 935 – 25 May 992) established an elite knightly retinue from within his army, which he depended upon for success in uniting the Lekhitic tribes and preserving the unity of his state. Documented proof exists of Mieszko I's successors utilizing such a retinue, as well.

Question:
Who also established this retinue as well?

Mieszko I's successors