Why did east Berlin leaders want to end access of their people to west Berlin?

East Berlin leaders wanted to end access to West Berlin to prevent a mass exodus of their citizens, who were increasingly fleeing to the West for better economic opportunities and political freedoms. The flow of people was undermining the legitimacy of the East German regime and its socialist ideals. By restricting access, they aimed to stabilize their population and maintain control over their society. The construction of the Berlin Wall in 1961 was a direct response to this crisis.