The United States military is preparing for the possibility of warfare not only in Earth's orbit but as far out as the moon, senior American military officials declared this week at a major defence conference near Washington. General Dan Caine, Chairperson of the Joint Chiefs of Staff and President Donald Trump's top military adviser, told service members and defence industry figures at the Air, Space and Cyber Conference that the US military must adapt now to be "prepared to fight, endure and win ... from the seabed to cislunar space" — a term referring to the vast region between high Earth orbit and the moon.

The declaration came days after Air Force Secretary Troy Meink made what was described as a historic first: publicly confirming that the United States has already deployed "on-orbit space control weapons" — that is, weapons stationed in space itself. Lieutenant General Gregory Gagnon, head of the Space Force's Combat Forces Command, told reporters that the push into this new military frontier is driven by a clear-eyed intelligence assessment: potential adversaries, most notably China, are actively pursuing military capabilities in space. China established its own dedicated military space force in 2024. In response to this week's announcements, a Chinese foreign ministry spokesperson urged Washington to "stop expanding its military preparations in outer space," stating that Beijing firmly supports the peaceful use of space and opposes its militarisation.

The Space Force, the newest branch of the US military, was created by Trump in 2019. Lieutenant General Gagnon announced plans to roughly double its size over the next five years, from approximately 12,500 to 25,000 service members, with about two-thirds of that growth concentrated in its Combat Forces Command. Officials framed these moves in terms of deterrence rather than aggression. "We have capabilities in the military because we are preparing to defend the nation," Gagnon said.

The announcements have nonetheless raised serious questions about international law. The 1967 Outer Space Treaty, signed during the Cold War, prohibits the placement of weapons of mass destruction in orbit and designates space for peaceful purposes. While the treaty does not explicitly ban all weapons, it has long underpinned an international understanding that space should remain non-militarised. When pressed on how US actions square with these obligations, Lieutenant General Gagnon said the Space Force would "continue to execute safe and responsible space operations" but declined to clarify policy on the use of kinetic weapons such as bullets or projectiles in space, directing questions to the Pentagon.

Why this matters: the open acknowledgement that the United States has placed weapons in orbit and is planning for combat scenarios near the moon marks a significant shift in how major powers discuss space. For decades, military space activity — even when extensive — was rarely spoken of in such direct terms. As both the US and China accelerate their space programmes, including lunar exploration with potential strategic dimensions, the absence of a clear updated international legal framework leaves the rules of any future conflict beyond Earth's atmosphere dangerously undefined.