It is incorrect that foreign propaganda is never sustained.
For example the United States government is currently engaged in a blanket of propaganda covering communications, social media and news outfit over the Middle East - they go so far as to create video games for the children there to play. The goal is a deradicalization of the Middle East - the vast majority of which now have turned against or are deeply suspicious of the United States (even NATO member Turkey).
How episodic propaganda operations are depends on the goal of the propaganda. Sometimes there is a specific ephemeral purpose (e.g. military deception), other times it is a short term goal (e.g. increase trust in gov't bonds) and other times it intends to be permanent or long lasting (e.g. America and Western culture is friendly to you and you would like to be a part of it).
For example the United States government is currently engaged in a blanket of propaganda covering communications, social media and news outfit over the Middle East - they go so far as to create video games for the children there to play. The goal is a deradicalization of the Middle East - the vast majority of which now have turned against or are deeply suspicious of the United States (even NATO member Turkey).
How episodic propaganda operations are depends on the goal of the propaganda. Sometimes there is a specific ephemeral purpose (e.g. military deception), other times it is a short term goal (e.g. increase trust in gov't bonds) and other times it intends to be permanent or long lasting (e.g. America and Western culture is friendly to you and you would like to be a part of it).