South Korean and U.S. troops held a live-fire exercise near the border with North Korea

South Korean and US militaries staged a major live-fire exercise near the border with North Korea on Thursday, defying the latter’s warning that it would not tolerate what it called an invasion rehearsal on its doorstep.

The exercise, the first of five rounds of live-fire drills to be held until mid-June, marks the 70th anniversary of the military alliance between Seoul and Washington. North Korea usually responds to such large-scale drills between South Korea and the US with missile and other weapons tests.

North Korea has tested more than 100 missiles since the start of 2022, but has not launched a single one since mid-April when it conducted a test of a solid-fuel intercontinental ballistic missile. It says its tests are a response to expanded military exercises between the United States and South Korea, but observers say North Korea is seeking to speed up its weapons development and eventually press for greater concessions from its rivals through diplomatic means.

The U.S.-South Korean live-fire exercise, known as the “Joint Destructive Fire Exercise,” is the largest training exercise of its kind. According to South Korea’s Defense Ministry, the exercises have been held 11 times since they began in 1977.

According to South Korea’s defense ministry, the exercise involved 2,500 troops and 610 weapons systems such as fighter jets, attack helicopters, drones, tanks and artillery from South Korea and the United States. The most recent exercise in 2017 involved around 2,000 troops and 250 weapon systems from both countries.

The drills simulated artillery and air strikes on North Korean military facilities on the front line in response to the attack.

The ministry said in a statement that South Korea would seek to establish “peace through overwhelming force” to counter North Korea’s threats.

North Korea has not yet responded to the start of the drills. Last Friday, its state media called the exercises a typical rehearsal for a war directed at North Korea and said it could not ignore the fact that the drills were taking place several kilometers from its border.

The North’s Korean Central News Agency said the US and South Korea would face unspecified retaliation for the drills.

Earlier this year, the militaries of South Korea and the United States held their largest field exercise in five years. The US also sent the nuclear-powered aircraft carrier USS Nimitz and nuclear-capable bombers to joint exercises with South Korea.

Moon Seong-mook, an analyst at the Seoul-based Korea National Strategy Research Institute, said North Korea could use the South Korean-US drills as a pretext to resume testing. He said domestic issues, such as North Korea’s push to boost agricultural production after rice planting begins, could still influence the decision on the weapons tests.

“North Korea cannot help but feel a certain burden because of the joint fire drills between South Korea and the United States, which are being held for the first time in six years,” Moon Seong Mook said.

US President Joe Biden and South Korean President Yoon Suk-yeol, who met last month, announced that they would take steps to strengthen deterrence capabilities. Mr. Biden also strongly warned that any nuclear attack by North Korea against the United States or its allies would “be the end of any regime” that would take such action.

Kim Yo Jong, the sister of North Korean leader Kim Jong Un, said the deal between Mr. Biden and Yoon Suk-yeol revealed the two countries’ “most hostile and aggressive willingness to take action” against North Korea. She threatened to further strengthen her country’s nuclear doctrine, saying that “the impossible dream of the US and South Korea will now face a more powerful entity.”

Concerns about North Korea’s nuclear program have increased since North Korea passed a law last year allowing for the preemptive use of nuclear weapons. Many foreign experts say that North Korea does not yet have operational nuclear missiles.