Secretary of Defense Jim Mattis has made a trip to South Korea and the DMZ where he made it known that North Korea has accelerated itself as nuclear threat. From Fox News:

“North Korea has accelerated the threat that it poses to its neighbors and the world through its illegal and unnecessary missile and nuclear weapons programs,” Mattis said.

Mattis said North Korea would be vastly overmatched by the firepower and cohesiveness of the decades-old U.S.-South Korean alliance.

“Make no mistake — any attack on the United States or our allies will be defeated, and any use of nuclear weapons by the North will be met with a massive military response that is effective and overwhelming,” he continued.

Mattis also insisted that the U.S. will not “accept North Korea as a nuclear power.”

At the same news conference, South Korean Defense Minister Song Young-moo explained that the two men have “agreed to further cooperation on strengthening Seoul’s defense capabilities, including lifting warhead payload limits on South Korean conventional missiles and supporting the country’s acquisition of ‘most advanced military assets.'”

He did not mention if this means nuclear-powered submarines, which some in the South Korean government want to get for the country. A few conservative politicians have advocated the U.S. return tactical nuclear weapons that were taken in the 1990s. Both Song and Mattis dismissed that idea. From The Associated Press:

“When considering national interest, it’s much better not to deploy them,” said Song, adding that the allies would have “sufficient means” to respond to a North Korean nuclear attack even without placing tactical nukes in the South. Mattis said current U.S. strategic assets are already providing nuclear deterrence and that the South Korean government has never approached him with the subject of tactical nukes.

Also discussed in the meeting were the conditions under which South Korea would be given wartime operational control of its forces. Currently, if war with the North broke out, the South’s forces would operate under the U.S.-led U.N. Command.

On Friday, Mattis made his first visit to the demilitarized zone that divides the Korean peninsula. From The Wall Street Journal:

“North Korean provocations continue to threaten regional and global security despite unanimous condemnation by the United Nations Security Council,” Mr. Mattis said in prepared remarks as he overlooked North Korea with Seoul’s defense minister at his side.

Mr. Mattis, making his first trip to the DMZ as defense secretary, reaffirmed the U.S. commitment to South Korea’s security. He also said that Washington’s goal “is not war, but rather the complete, verifiable and irreversible denuclearization of the Korean Peninsula.”

North Korea has shot two missiles over Japan since August and successfully tested a nuclear bomb. Fox News reported at the time:

. . . . The test was estimated to have a yield of 100 kilotons, meaning a blast that was four to five times more powerful than the explosion in Nagasaki, Japan, in 1945, a South Korean defense official told the country’s Yonhap News Agency.

. . . . Just hours before Sunday’s test, photos emerged showing the North Korean dictator inspecting a new thermonuclear warhead in a lab. This would be North Korea’s sixth nuclear test and first since September 2016.