The answer to the question above is. A. the enormous expansion of the military industry during and after World War II.
The United States was “compelled to form a permanent armaments industry” and a huge military force.
He clearly admitted that the Cold War made clear the “imperative need for this development,” but he was anxiously concerned about “the acquisition of unwarranted influence…by the military-industrial complex which has developed in the post-World War II years..”