Secretary of Defense, James Mattis, made a clear statement regarding North Korea’s nuclear missile program on Friday, while continuing his visit in the South Korean capital, Seoul.

Mattis explained in no uncertain terms that the use of nuclear weapons by North Korea against the United States or any of its allies would be met with an “effective and overwhelming” response.

The United States has long considered both South Korea and Japan to be beneath the American “nuclear umbrella,” or portions of the world that, if under nuclear attack, would be met with the same nuclear response an attack on the United States itself would warrant.  However, Mattis’ decision to address North Korea directly during a visit to the South Korean capital marks a slight departure from the norm, as such declarations are usually made in a more nuanced manner.

“North Korea continues to launch missiles, develop its nuclear weapons program, and engage in threatening rhetoric and behavior,” Mattis said during a public meeting with his South Korean counterpart, Defense Minister Han Min Koo.

“We stand with our peace-loving Republic of Korea ally to maintain stability on the peninsula and in the region,” he added. “America’s commitments to defending our allies and to upholding our extended deterrence guarantees remain ironclad: Any attack on the United States, or our allies, will be defeated, and any use of nuclear weapons would be met with a response that would be effective and overwhelming.”

Mattis’ statement adds emphasis to the very reason for his visit, as South Korea has grown concerned about the Unites States’ commitment to honoring their alliance after now-President Trump expressed his distaste for the cost of maintaining the sizeable American force located in South Korea.  There are currently 28,500 U.S. troops permanently based in South Korea, with another 50,000 nearby in Japan.  These forces serve as a means of defense for the two nations as well as international operating bases for the United States to maintain its ability to respond to global threats.

During the visit, Mattis discussed deployment timetables for the THAAD missile defense system that the United States has promised to position in South Korea as a means by which to defend against any potential nuclear strikes coming from their aggressive northern neighbors.  The THAAD, or Theater High-Altitude Area Defense system, will be placed in Japan as well in order to protect each respective nation, and the US forces stationed within.

Strengthening partnerships with South Korea and Japan seems to be high among President Trump’s priorities despite his previous complaints about the cost associated with maintaining a permanent presence in each nation.  His newfound appreciation for these Asian alliances likely comes as a result of growing tensions between the United States and economic powerhouse, China, who has put forth significant effort toward becoming a military power in recent years as well.