United States Ship Ronald Reagan, a 97,000-ton aircraft carrier, is plying the waters off South Korea in the biggest display of American military might in and around the Korean peninsula in more than five years.

American fighter planes and helicopters are taking off from the deck of the carrier in close coordination with South Korean aircraft and warships as the military forces of the two countries wind up large-scale exercises intended to show they can work together and discourage North Korea’s Kim Jong-un from living up to his threats.

“One of the main lessons from the battlefields of Europe is interoperability,” the commander of U.S. Forces Korea, General Paul LaCamera, said after 10 days of ground exercises before the Ronald Reagan arrived at Busan, South Korea’s largest port, for its role in the war games.

General LaCamera, in an online conversation staged by the Institute for Corean-American Studies in Philadelphia, seemed relieved to see American and South Korean forces involved in live war games instead of computerized exercises. The slogan “‘Fight Tonight’ cannot just be a bumper sticker,” he said, picking up on the watchword of American commanders that America’s troops in South Korea must always be “ready to fight tonight.”

“There’s got to be real teeth behind those words,” the general, also commander of the United Nations Command and the Combined Forces Command, including America’s 28,500 troops and Korea’s armed forces, said. They’re all braced for the possibility that the North’s strongman might eventually make good on his promises to challenge the Americans and South Koreans militarily — or at least to stage another nuclear test.

The presence of the Ronald Reagan as the centerpiece of the latest joint exercises dramatized the urgency of the general’s remarks. Also participating in the war games are the destroyers and supply ships in the carrier strike group that accompany it wherever it goes, plus South Korean vessels.

The commander of the strike group, Rear Admiral Buzz Donnelly, preferred not to see the Ronald Reagan’s visit to Busan as having much to do directly with North Korea. Rather, he told reporters, it was there in “a clear and unambiguous demonstration of U.S. commitment to the alliance.”

The importance of the Ronald Reagan in the military exercises was obvious when he remarked, in carefully formal wording, that America’s interactions with the South Korean navy “are tactically purposeful in developing interoperability to ensure credible combat power.”

General LaCamera put all the exercises in context: “It is imperative to remember the Korean War has not ended,” he said, citing the armistice of July 1953 that stopped the shooting but did not mean the combatants, including the two Koreas, the Chinese, and the Americans, had achieved a permanent peace.