The correct answer is - Proxy wars.
During the Cold War period, the so called proxy wars, used by the United States and the Soviet Union, were a very common thing. In this type of war, the country itself doesn't involve its military in a direct way, but instead it hires people in the country of interest, and also infiltrates its own people. They fund, train, propagate, and that is in order so that they can take down a government without being directly military involved, as that will mean that they will face sanctions.