We learned earlier this week that the US has deployed its first secretive space weapon in orbit above Earth. Now, the Chairman of the Joint Chiefs of Staff says the United States military must be prepared to one day fight battles on the moon. Or real close to the moon, depending on how the term “cislunar” is read.

As reported by Defense One, General Dan Caine made the following remarks in his recent keynote address at the Air, Space, and Cyber Conference.

“Our task, my friends, is to adapt right now, so the Joint Force is prepared to fight, endure, and win, in global contested environments, from the seabed to cislunar space,” Caine said, later adding that “today’s modern battlefield operates from the seabed to cislunar space.”

But as Defense One points out, the definition of cislunar is vague when it comes to US law. Is it the region of space just outside of the moon or does it include the surface of the moon itself? Depends on who you ask, it seems.

There are, however, existing international agreements meant to restrict human activity on the moon to be “exclusively for peaceful purposes.”

The US already agreed to the Outer Space Treaty of 1967 that bans the building of lunar military bases, as well as any weapons testing or military exercises on the moon. Countries that signed the treaty can only use military personnel on the moon for “scientific research or for any other peaceful purposes shall not be prohibited.”

Concerns about the possibility of a future conflict in space or on the moon stems from the ongoing rivalry between the US and China.

“The U.S. needs better capabilities in cislunar space to ensure China complies with that obligation and doesn’t militarize the moon,” Aaron Brynildson, a space law professor at the University of Mississippi, told Defense One. “There’s a real coverage gap by the U.S. that needs closing.”

Brynildson fears it might already be too late to clarify existing space law language in regards to military actions outside of our planet: “Ultimately, I think the first space conflict might be the time when most of these rules get written.”

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