The Korean war had a purpose but it had largely failed.
Step-by-step explanation:
Truman can and cannot be blamed for the war as he had formulated this policy of attacking in per preemptive measures to control the spread of communism that had plagued the US for so long.
At the same time the nature of the policy was such that it has led to the development of the US in certain senses.
So, as all things in history it is a two way thing and often based around the perspective one has of things.
The war itself was not a success in terms of containing communism as North Korea was out of grasp.