Donald P. Steury, in his book "The Berlin Wall: 13 August 1961 - 9 November 1989," argues that the building of the Berlin Wall marked a significant shift in Soviet policy towards the West. According to Steury, the decision to construct the wall reflected a new approach by Soviet leaders, who were increasingly concerned about the erosion of Soviet influence in East Germany and the spread of Western ideas and values.Prior to the construction of the wall, the Soviet Union had pursued a policy of coexistence with the West, seeking to maintain a balance of power and avoid direct conflict. However, as tensions between East and West began to escalate in the late 1950s and early 1960s, Soviet leaders became more assertive in their efforts to control East Germany and prevent the spread of Western influence.The construction of the Berlin Wall was a dramatic demonstration of this shift in Soviet policy. By building a physical barrier between East and West Berlin, the Soviet Union was signaling that it was willing to use force to maintain control and prevent the spread of Western influence. The wall also represented a rejection of the idea of coexistence with the West and a return to a more confrontational approach.Overall, Steury suggests that the building of the Berlin Wall marked a significant turning point in the Cold War and signaled a new era of Soviet aggression towards the West.