"From 1930 onwards, the Party and police officials feared the "social disorder" caused by the upheavals of forced collectivization of peasants and the resulting famine of 1932–1933, as well as the massive and uncontrolled migration of millions of peasants into cities.

The threat of war heightened Stalin's perception of marginal and politically suspect populations as the potential source of an uprising in case of invasion. He began to plan for the preventive elimination of such potential recruits for a mythical "FIFTH COLUMN of wreckers, terrorists and spies."

https://en.wikipedia.org/wiki/Collectivization_in_the_Soviet_Union

I thought this was interesting, mentioning a fifth column.