American troops need to prepare for combat not only in Earth’s orbit but around the moon, Donald Trump’s top military adviser said on Wednesday, looking ahead to a new frontier in warfare after the US revealed for the first time that it has deployed weapons in space.

Gen Dan Caine, chairman of the joint chiefs of staff, told service members and industry figures at the Air, Space and Cyber Conference outside Washington that the US military should adapt now so it “is prepared to fight, endure and win ... from the seabed to cislunar space”.

Cislunar space is a term that describes the region between the earth’s surface and the moon.

The Space Force, the newest military service, which was created by Trump in 2019, is preparing to fight in space and around the moon because “humanity is advancing deeper into space – the Space Force’s job is to help be prepared to defend US interests”, Lt Gen Gregory Gagnon, head of the force’s Combat Forces Command, told reporters separately.

The announcement that the US military is ready to fight in the area between high Earth orbit and the moon itself comes days after air force secretary Troy Meink revealed at the same conference that the US has fielded “on-orbit space control weapons”.

The spate of announcements about space weaponry from military officials over recent days flies in the face of long-standing conventions and international understandings that have held outer space as only to be used for peaceful purposes and remain non-militarized.

The Space Force says potential US foes may look to turn space into a battleground

While multiple nations, including the US, have demonstrated the ability to shoot down satellites in Earth orbit, those demonstrations have taken place from the ground against their own satellites.

However, according to Gagnon, “the intelligence community has been clear that potential adversaries have been seeking to extend warfare into space” and that the US military needs to react.

“Our potential adversaries such as the PRC are actively pursuing activities in the system, in parts of space,” Gagnon said, referring to the People’s Republic of China, the country’s official name.

China established its own military space troops in 2024, charging them with boosting capability to manage space crises.

When asked about the US announcement on deploying weapons in space, Chinese foreign ministry spokesperson Guo Jiakun told reporters Tuesday that “China always upholds the peaceful use of outer space, maintains outer space security and opposes the weaponization, militarization and an arms race in outer space”.

Guo also urged the US to “stop expanding its military preparations in outer space”.

It is not clear whether deploying weapons in space or possible plans to use them around the moon will run afoul of international treaties that prevent the militarization of space.

The Outer Space treaty of 1967, which the US and China have signed, says celestial objects such as the moon are to be used “exclusively for peaceful purposes,” nuclear weapons cannot be placed in space and countries are “liable for damage caused by their space objects”.

There was a renewed push two years ago to further bolster anti-militarization measures in the United Nations following US reports that Russia was developing a space-based weapon.

Gagnon also says the US aims to double the size of the Space Force over the next five years – to roughly 25,000 service members – and that about two-thirds of that growth would be focused on Combat Forces Command.