Answer:
The Truman doctrine was issued by President Harry S. Truman.
Step-by-step explanation:
According to this "Truman's doctrine" united states would provide Military, Political and economic support to all the democratic countries which are under the threat of internal as well as external soviet aggression or any Authoritarian forces.
This stand of Truman policy changes the stance of the united states of withdrawal from other regional conflicts to directly get involved in the conflict zone of others which are far away from the united states, Vietnam war is the correct example of this doctrine.
Truman argued, united states could not longer stand-still and keep watch the soviet aggression of expansion in democratic countries.