What caused the reforms of the mid-16th century?

The reforms of the 16th century were carried out mainly by Ivan 4. He strove to renew the state structure and the system of administration. The reasons for this were internal and external factors. Initially, the country needed development due to lagging behind the advanced states. Especially for this, the estate-representative body of the Chosen Rada was introduced. Russia needed territories that could lead her to the sea and to the trade routes of Europe. Ivan 4 strove for absolute monarchy. In the second half of the reign, he introduced the oprichnina.