 Under pressure to proceed with the ABM program after it became clear that the Soviets had begun a similar project, McNamara finally agreed to a "light" system which he believed could protect against the far smaller number of Chinese missiles.However, he never believed it was wise for the United States to move in that direction because of psychological risks of relying too much on nuclear weaponry and that there would be pressure from many directions to build a larger system than would be militarily effective.He always believed that the best defense strategy for the U.S. was a parity of mutually assured destruction with the Soviet Union.