There is nothing inevitable about the U.S. winning wars, and on that point the Pentagon’s new missile defense review is alarming. Russia and China are ramping up investments in sophisticated technologies while America is spending less on defending itself. One urgent priority: A constellation of space sensors that could shore up U.S. missile defenses.

Paul Gigot interviews General Jack Keane.

More than 20 nations have offensive missile technology, the Defense Department notes in its review released last month. China can already threaten the U.S. with some 125 nuclear missiles. Iran’s medium-range missiles threaten Israel and Europe, and the report notes that Iran “has transferred missile systems to terrorist organizations,” which use them on U.S. allies. Russia is violating the 1987 INF nuclear-missile treaty.

China has been increasing its medium- and intermediate-range missile stocks. “This includes sophisticated anti-ship missiles that pose a direct threat to U.S. aircraft carriers,” the report says. The U.S. has dominated the seas for decades with aircraft carriers, yet Chinese missiles could keep carrier strike groups from operating in the Western Pacific.

Another threat are hypersonic missiles in development by China and Russia, and the Pentagon notes that Russian leaders claim to have such a hypersonic glide vehicle. These missiles fly rapidly at lower altitudes and are more maneuverable, which would help them elude U.S. missile defenses.

The U.S. currently employs satellites that can track a fraction of a missile’s trajectory, and as Todd Harrison of the Center for Strategic and International Studies puts it: “If you can’t see it, you can’t shoot it.” A network of sensors in space could track the entire life of the missile and thus allow for more precise targeting from interceptors.

Yet this good idea has been trapped for years in the wet cement known as U.S. bureaucracy. The Obama Administration’s missile defense review in 2010 said space sensors would “greatly reduce the need for terrestrial sensors and the size of deployable missile defense systems,” while calling the project a “long-term effort.” Congress last year appropriated $120 million for space missile defense systems, a down payment the Pentagon shouldn’t waste on procurement or administrative bloat.

President Trump said at the review’s rollout that his fiscal 2020 budget will include money for the sensor layer, calling it “a very, very big part of our defense and obviously, of our offense.” But House Democrats want to cut defense spending and plow the money into infrastructure or green energy. The left will say the Pentagon needs better spending priorities, but the crucial political trade-off isn’t between more missiles or more ships, but between more spending on defense or more on the social programs and entitlements that have relentlessly been squeezing defense.

Meantime, you can bet that adversaries will continue to exploit America’s lack of political will as an opportunity to catch up on every technology from missiles to jet fighters. A better missile defense system is not a project you want to be finishing after the country needs protection.