What does King advocate as a countermeasure to physical force?

Soul Force.

Explanation:

In American Dream speech  of Martin Luther King he says “We will meet your physical force with soul force.”

Soul force is a way to counter aggression by being calm and peaceful. We have seen many world leaders using this method to get their needs fulfilled. Gandhi was the pioneer of it, he used non violent protests in response to the tyranny of British Imperialism. Same was used by Nelson Mandela. And Martin Luther King also prioritized this method to overcome their issues.

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