Question

What was the underlying cause of the Cold War

Answer 1

Russia's unwillingness to let go of Eastern European countries after the war. (And the fact that new President Truman and Prime Minister Attlee were unwilling to take the hard line with Stalin that their predecessors had)

Armament race and brinkmanship (Every time one country developed a weapon the other would become afraid and develop a better one...etc.)

Differing communist and capitalist ideology

Race to become the superpower