Picture this: A Chinese fighter jet accidentally crashes into a Navy P-8 Poseidon surveillance plane while attempting to buzz it over the South China Sea, killing all on board both aircraft. Fearing U.S. retaliation, China goes a relatively unexpected route: It uses surface-to-air missiles to shoot numerous U.S. satellites out of the heavens in quick succession.

Very quickly, the Navy is forced to navigate the Pacific with little use of GPS and degraded communications, causing chaos and uncertainty. The Chinese strikes also have knocked out some of the Pentagon’s ability to control its arsenal of precision-guided weapons.

None of this has happened. But the hypothetical scenario points out the reliance the Pentagon has on space and the military technology it keeps in it. Satellites have soared over the earth’s atmosphere for decades, providing the United States with a huge advantage militarily, even at a time when the conventional weapons U.S. rivals have are formidable.

A new report released on Wednesday by the Center for a New American Security highlights the vulnerabilities the Pentagon has in space, and calls for a shift in strategy to safeguard it and prepare for conflict there. It’s written by senior fellow Elbridge Colby, a former member of the presidential campaign staff of Gov. W. Mitt Romney (R.-Mass.), and argues that potential adversaries like China and Russia have noticed the degree to which the United States is reliant on its “space architecture,” and begun to seek ways to threaten it.

“Indeed, many observers have noted that these potential opponents judge the U.S. space architecture to be the Achilles’ heel’ of U.S. military power, in light of the depth of American reliance on theses systems and the vulnerability of the U.S. military satellite architecture,” the report said.

Threats to satellites include not only missiles, but also cyber and electronic attacks that could disable them. In effect, Colby argues, “space is becoming a domain like any other — air, sea, land, and electromagnetic — in which the United States will have to compete and fight the ability to access and exploit the domain rather assume safe and uncontested passage within and use of it.”

The Pentagon already has begun to prepare in response. Last year, for example, Defense Secretary Ashton B. Carter directed the military to begin looking at reducing its reliance on GPS satellites, arguing that the Defense Department probably won’t buy them within 20 years.

“Here’s a sentiment and a prediction for you: I hate GPS,” Carter said in a exchange of questions on a blog produced by the investment firm Andreessen Horowitz. “The idea that we are all hooked to a satellite — formerly bought by me to my great resentment — in a semi-synchronous orbit that that doesn’t work in certain circumstances, does not work indoors or in valleys in Afghanistan, is ridiculous.”