A more thorough explanation:

Indirect aggression is a type of aggression that is carried out by means other than a state's regular armed forces. This can include delictual acts that are conducted vicariously by the aggressor state through third parties, or delictual acts taken directly by the governing authorities of a state against another state or vicariously through third-party groups. In both cases, the aggression endangers the essential rights of a state upon which its security depends.

For example, economic pressures on other states, demands couched in traditional diplomatic terms but laden with implied threats to compel action or inaction, fifth column activities, propaganda urging another state's peoples to rise against their government, aiding and abetting of rebel bands intent on overthrowing another government, and a wide range of other modern techniques can be considered indirect aggression if they are delicts at international law and directed against the sovereign independence of a state.

These examples illustrate how indirect aggression can be used as a method of constraint carried on by the aggressor state without directly involving its regular armed forces. It is important to recognize indirect aggression as a form of aggression in international law to protect the essential rights and security of states.