The United States needs to prepare for war in space. For many years, conventional wisdom held that readying to fight in space was unduly provocative and destabilizing. Many hoped that military competition and war could be confined to Earth.

This may or may not have been a noble aspiration, but it is no longer in touch with reality. The United States therefore needs to face facts and develop the strategy and capabilities to fight and prevail in a war that reaches into space.

The basic reason why is that potential US adversaries — and particularly formidable nuclear-armed ones like Russia and China — are gearing up to take any war with the United States into space. China has conducted several anti-satellite missile tests in recent years, including one out to geosynchronous orbit, where many crucial US satellites are located.

Russia, meanwhile, has openly boasted of its anti-satellite capabilities, and news sources reported that it successfully tested an anti-satellite missile late last year. As a result, of these efforts, a senior US Air Force general reported last year that "we are quickly approaching the point where every satellite in every orbit can be threatened."

Potential US opponents are doing this because they recognize how greatly the United States relies on its space architecture for its military advantages. Indeed, so profound is American reliance that many view space as the "Achilles' heel" of the US military.

Washington is particularly dependent on its space assets to project military power over long distances, yet this is precisely what US armed forces needs to do to credibly and effectively defend US allies and interests in places like the Western Pacific and Eastern Europe.

US forces rely on space assets to communicate (including securely), position themselves and navigate, collect intelligence, target adversaries, and for a wide range of other crucial military functions. On top of this, US satellites are "juicy targets," built during an era when space was largely considered a safe sanctuary beyond adversaries' reach.

So the United States is deeply reliant on its space architecture, and yet this vital asset is very vulnerable. And not just to projectiles that would create controversial space debris (as in the movie Gravity). Rather, an increasingly wide gamut of nations can attack US satellites through non-kinetic, limitable, and even reversible techniques.

These methods include jamming communications with the satellite, blinding or dazzling it with a laser, or cyber-attacking its computer systems. This means that an opponent is likely to have ways of going after US satellites in militarily significant ways that don’t necessarily seem massively escalatory. Given that satellites "have no mothers," how angry are the American people going to be if one gets disabled by jamming or cyber-attack, even if the satellite is a crucial asset?

This, then, is the problem. Fortunately, the defense establishment has begun to respond to it. But the government’s thus-far commendable efforts do not yet appear to be part of a coherent strategy. Yet, if the United States doesn’t adapt its space architecture within such a strategy, it risks wasting money or even just presenting just a slightly tougher target to adversaries.

Better defenses, more resilience and the like won't change the fact that attacking satellites is likely to be easier than defending them and cheaper than launching replacements.

Rather, The United States needs a strategy for space that recognizes that vulnerability isn’t going away, and but that seeks to convince adversaries not to exploit those vulnerabilities. That means issuing tailored threats to respond to an enemy’s attack in space — including through retaliation on Earth — and developing the capabilities to back up those threats; making our space architecture less of a "juicy target" by improving defenses and resilience; preparing our military to fight effectively with reduced access to space; and promoting international perceptions that carrying a war into space and attacking essentially innocent satellites is condemnable.

Basically, it means changing from a stance of hoping that adversaries won’t risk the opprobrium of expanding a war into space to , by preparing for them to do so, convincing them that doing so – and especially doing so in militarily significant ways – would be too risky and costly to undertake.

The era of unchallenged US dominance of space is over. The United States therefore needs to prepare for a war that extends into space – and to prevail nonetheless. Failing to do so risks a capable adversary thinking that it can shatter the American military's glass jaw — if it does not cry out for it.

Elbridge Colby is the Robert M. Gates senior fellow at the Center for a New American Security. He authored is the author of the January 2016 CNAS report "From Sanctuary to Battlefield: A Framework for a U.S. Defense and Deterrence Strategy for Space."