American and South Korean troops are poised to challenge the inflammatory rhetoric and dire threats of North Korea’s leader, Kim Jong-un, with 10 days of joint exercises beginning Monday. 

The war games, featuring all services, are expected to come close but not too close to the North-South line in an atmosphere of mounting tension that has top officers worried that Mr. Kim may actually live up to his word and hurl more than rhetoric against his enemies.

The commander of the U.S. Strategic Command, General Anthony Cotton, sees North Korea’s increasingly tight relations with America’s greatest potential foes, Russia and China, as adding “new layers of complexity to our strategic calculus.” More simply, he told the Senate Armed Services Committee, the rising confrontation “raises the possibility of simultaneous conflicts with multiple nuclear-armed adversaries.” 

That scenario adds to the urgency of the upcoming exercises, a semi-annual show called “Freedom Shield” that South Korea’s conservative president, Yoon Suk-yeol, has enthusiastically endorsed after his liberal predecessor, Moon Jae-in, had restricted them largely to computer-driven war games. Mr. Kim has added to the sense of danger by cutting off all dialogue with Washington and Seoul, vowing to deploy nuclear weapons if needed, and proclaiming South Korea the North’s “primary foe.” 

A longtime Korea analyst at the RAND Corporation, Bruce Bennett, sees Mr. Kim as scheming to get the Americans and South Koreans to appear to be about to attack the North. He may be looking for a pretext to strike back, believing that China and Russia, the two powers on which his grandfather, Kim Il Sung, needed to stave off defeat in the Korean War, would be on his side. 

“The vehemence of Kim’s latest threats,” Mr. Bennett said, may mean he’s hoping that Seoul and Washington “will overreact to his threats of attack on and annihilation of” South Korea. 

“An overreaction would give him justification for some level of escalation,” Mr. Bennett, writing in the National Interest, said. He then could “claim that President Yoon is a warmonger.” 

That South Korean and American troops are joining in such significant exercises in the month before what are likely to be pivotal elections for the South’s national assembly adds to the risks of a strong North Korean response. 

Mr. Yoon was elected president by a margin of less than 1 percent two years ago, and the opposition Democratic Party still has slightly more seats than his People Power Party in the assembly. Mr. Kim could hope to undermine Mr. Yoon’s party in the April election, Mr. Bennett said, making it difficult for Mr. Yoon  to maintain a strong policy vis-à-vis North Korea. 

Mr. Yoon, though, may also want to project his image as a tough guy standing up to the North as opposed to his predecessor, who sought dialogue. Mr. Kim saw Mr. Moon three times in 2018, when Mr. Kim also met President Trump in Singapore. but he refused to see Mr. Moon after the failure of the second Trump-Kim summit at Hanoi five years ago. 

A primary purpose of the upcoming war games, American and South Korean military officials said, will be to identify as targets the sites from which North Korea has test-fired more than 100 missiles over the past two-plus years. No way, they said, will they approach the demilitarized zone between the two Koreas — though the North is sure to accuse Washington and Seoul of plotting an “invasion.”