Defense Secretary Jim Mattis, left, accompanied by Joint Chiefs Chairman Gen. Joseph Dunford, speaks to media members at the White House on Sept. 3. (Pablo Martinez Monsivais/AP)
 
Defense Secretary Jim Mattis acknowledged Monday that his South Korean counterpart inquired recently about reintroducing tactical nuclear weapons on the Korean Peninsula, a move that could take tensions with North Korea to a new high.
Mattis, speaking to reporters at the Pentagon, confirmed that he and Defense Minister Song Young-moo discussed the weapons during an Aug. 30 visit in Washington. The Pentagon chief did not say whether he’d support such an idea, however. Song has advocated for the move, calling it an “alternative worth a full review.”
[South Korea’s defense minister suggests bringing back tactical U.S. nuclear weapons]
Asked about the exchange, Mattis said that “we discussed the option,” but he declined to elaborate.
“We have open dialogue with our allies on any issue they want to bring up,” Mattis said.
The United States maintained nuclear weapons in South Korea during much of the Cold War, but President George H.W. Bush ordered their removal after the Soviet Union’s fall in 1991. At the time, Bush saw it as a way of bolstering demands that North Korea not pursue its own nuclear weapons.
South Korean President Moon Jae-in has said several times that he is against the return of nuclear weapons, but he faces opposition on that point from many conservative leaders in his country. Tactical nuclear weapons, sometimes called nonstrategic nukes, are designed to strike military targets such as bunkers and tunnels but are still considered immensely powerful in their own right and a potential gateway to larger nuclear attacks.
Some senior U.S. military officials, such as Air Force Gen. Paul J. Selva, vice chairman of the Joint Chiefs of Staff, have advocated generally for more “small-yield” nuclear weapons, arguing that the United States needs the ability to respond to an attack using a smaller nuclear bomb with something of similar size.

But Air Force Gen. John Hyten, who oversees U.S. nuclear weapons as the chief of U.S. Strategic Command, took exception Thursday to calling even smaller nuclear weapons tactical. Speaking with reporters at his headquarters in Nebraska, he called the phrase a misnomer and “actually a very dangerous term” because there are significant consequences to using nuclear weapons in any format.
“To call it a tactical weapon brings into the possibility that there could be a nuclear weapon employed on a battlefield for a tactical effect,” Hyten said. “It’s a not a tactical effect, and if somebody employs what is a nonstrategic or tactical nuclear weapon, the United States will respond strategically, not tactically, because they have now crossed a line, a line that has not been crossed since 1945.”
Mattis said last week that he would not discuss whether he is looking at reintroducing nuclear weapons in South Korea.
“It’s simply a longstanding policy so the enemy … our adversaries never know where they’re at,” he said. “It’s part of the deterrent that they cannot target them all. There’s always a great big question mark.”