JFK's 1961 inaugural address came at the height of the Cold War, in which America was deep in an arms race with the Soviet Union. His primary concern at that point was presenting America as a powerful nation while encouraging America and all nations, enemies and allies alike, to work out our problems diplomatically. Thus, its tones were those of strength, compassion, and hope and belief in the goodness and power of Americans working together.
He uses classic rhetoric to express these ideas, making this speech one of the most memorable inaugural addresses of all time. To express strength, he includes this now-classic line: "Let every nation know, whether it wishes us well or ill, that we shall pay any price, bear any burden, meet any hardship, support any friend, oppose any foe, in order to assure the survival and the success of liberty." In other words, while we aren't planning to go to war, we will if we have to. He speaks primarily to Americans who are "tempered by war, disciplined by a hard and bitter peace, [and] proud of our ancient heritage"--primarily strong, independent, proud people--but also to all other nations.
He pledges help to those who need it around the world and makes a point of saying that we aren't helping because we're trying to prove we're as good as or better than our Communist enemies, but "because it is right." He pledges to help all of our southern neighbors to "assist free men and free governments in casting off the chains of poverty." He also addresses those nations who are our adversaries, urging them in several paragraphs to "let both sides" looks for our similarities and not our differences, have serious discussions about the control of arms, to use science for good and not evil, and to "let both sides join in creating a new endeavor, not a new balance of power, but a new world of law, where the strong are just and the weak secure and the peace preserved."
He ends with hope, saying that although "the trumpet calls us again" and it is "a call to bear the burden of a long twilight struggle, year in and year out, 'rejoicing in hope, patient in tribulation.'" And even though he thought us in a time of "maximum danger," he believed that "the energy, the faith, the devotion which we bring to this endeavor will light our country and all who serve it—and the glow from that fire can truly light the world."
The most powerful words of this speech occur after this call to national cooperation: "And so, my fellow Americans: ask not what your country can do for you—ask what you can do for your country."