Answer:
It will start the nuclear war between U. S and Soviet union.
Explanation:
President Truman's refusal to use a nuclear weapon against the Soviet-backed Chinese during the Korean War because Soviet union was a also a nuclear power and this will leads to nuclear war between both countries and both countries were destroyed. Nuclear weapon causes great destruction in the area and wipeout everything that comes in their path so that's why the President Truman refused to use the nuclear weapon in the Korean war.
