Please answer a question about the following article about Dwight D. Eisenhower:

In the immediate years after Eisenhower left office, his reputation declined. He was widely seen by critics as an inactive, uninspiring, golf-playing president compared to his vigorous young successor. Despite his unprecedented use of Army troops to enforce a federal desegregation order at Central High School in Little Rock, Eisenhower was criticized for his reluctance to support the civil rights movement to the degree that activists wanted. Eisenhower also attracted criticism for his handling of the 1960 U-2 incident and the associated international embarrassment, for the Soviet Union's perceived leadership in the nuclear arms race and the Space Race, and for his failure to publicly oppose McCarthyism.

What nation was considered the leader in the nuclear arms race?
Soviet Union