What did the leaders of the soviet union feel would provide the most protection for their country

By having some pro-communist (коммунист) joined together on their borders, such as China or North Korea.

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.