This posting describes the relationship of containment and NSC-68 to the purpose of American involvement in the Korean War.
Since the topic is so vast, please allow my brainstorming to help you with your essay formation. Once you write it, I am more than happy to edit as well. Please send the draft to me for editing.
First, as you overview the role of NSC-68 and events leading to the Korean War, please note that it marked a major shift in foreign policy. It moved America to a more definitive containment policy based on the loss of China, initial Soviet nuclear explosions, the Alger Hiss case, etc.
Research also looks at the purpose of its development. Please suggest its origins in order to maintain a check on the "expansionist designs of the Soviet Union through economic, military, diplomatic, and political means " (http://www.answers.com/topic/containment).
Other pertinent background data might be helpful for you to reference. For example, NSC-68 was conceived by Paul Nitze, the chief author, and George Kennan soon after World War II. Please also note how the Truman Doctrine in 1947 further facilitated the basic goals of the document as well as the European Recovery Program (ERP). Since these areas overlap, you could even add this part to effects or long-term impact.
As mentioned, please also show its purpose was further suggested as a prevention tactic. For example, Kennan argued that "communist influence should be contained within existing territorial limits, either by armed intervention or, more often, by economic and technical assistance" (www.mtholyoke.edu/acad/intrel/nsc-68/nsc68-1.htm).
As you further look at its goals and premises, please also note that NSC-68 demanded various elements. First, it was a "policy of calculated and gradual coercion; its aim was to force a "retraction" of Soviet power--to get the Soviets to "recede" by creating "situations of strength" (www.mtholyoke.edu/acad/intrel/nsc-68/sec2.doc). It was definitely forceful.
In addition, you could also note that NSC-68 aimed for "a dramatic rollback of Soviet power" (http://novaonline.nv.cc.va.us/eli/evans/HIS242/Notes/NSC68.html). It was deliberate in its attempts to "reduce the power and influence of the USSR to limits which no longer constitute a threat to the peace, national independence, and stability of the world family of nations" ...
This document discusses containment and NSC-68 before the Korean War.