Which is a common tactic used in proxy wars? encouraging opposing powers' citizens to emigrate sponsoring wars of liberation and revolutions controlling another country secretly buying weapons in preparation for domestic warfare

sponsoring wars of liberation and revolutions

Explanation:

In a proxy war, you want your side to win in a particular country. To do that, you can often sponsor revolutions to get your people in power.

Sponsoring wars of liberation and revolutions

Explanation:

A proxy war is a type of war which takes place when two or more powers make use of third parties as substitutes, instead of directly going to battle.

Even though superpowers have sometimes used entire countries as subsidiaries, mercenaries, guerrillas, terrorists and spies are commonly chosen to indirectly beat the opponent down. The goal is to damage, weaken or disrupt the other power without ending up in an open conflict.