With overall federal budget expanding steadily year after year, you’d think not one category of spending has had to suffer. Surely everything that can be funded has all the money it could want or need — and then some.

But you’d be wrong. When it comes to defense spending, it’s a different story. Lawmakers that can’t bring themselves to make tough but necessary cuts elsewhere, even in areas of dubious federal responsibility, suddenly find they’re able to say “no” when it comes to something as vital as our national security.

A variety of cuts have taken their toll. Readiness is slipping. Troops are taking more and longer tours of duty. Equipment is being used well past its intended life. Our military is like an edifice that looks great from the outside, but is being eaten away by termites. Everything appears fine and normal — until one day it’s put to the test and found wanting.

Not because our troops aren’t the best. They are. It’s because of the cuts they’re being forced to deal with. “For years,” defense expert Frederico Bartels writes, “the defense budget prioritized short-term readiness over modernization and recapitalization of the force, resulting in a military that is growing old and tired.”

When he testified recently before the House Armed Services Committee, Defense Secretary James Mattis said the first priority of the fiscal year 2018 defense budget would be to fix near-term readiness problems. Rebuilding the military would come after that — in 2019 and beyond.

Frankly, though, we can’t wait to address the rebuilding. Our own military has been struggling for too long now, thanks to arbitrarily low levels of funding imposed by the Budget Control Act of 2011. All the while, we’ve been asking it to do more. But a high tempo of operations with a shrinking, aging and less-ready force is an unsustainable combination.

Consider how U.S. military power is graded in the Heritage Foundation’s 2017 Index of Military Strength. On a scale with five ratings (very strong, strong, marginal, weak and very weak), no branch ranks above “marginal” — and one (the Army) is “weak.”

Unfortunately, while funding took a holiday, worldwide threats have not. Russia and China continue to sink a lot of money into modernizing and expanding their military capabilities. North Korea has been rattling its nuclear saber with even more noise than usual. And the terrorist threat isn’t going away tomorrow.

That’s why it’s good the Senate and the House Armed Services committees have authorized more resources for the Department of Defense than what the Trump administration asked for. It’s an encouraging sign that lawmakers recognize how bad the situation is, and are prepared to do something about it.

But we have to keep pressing Congress to do the right thing. After all, we’re in this situation precisely because lawmakers have refused time and again to prioritize, and make hard decisions when it comes to spending.

Members of Congress need not resign themselves to passing another bad budget deal that increases both defense and non-defense spending. Instead, they should take this opportunity to prioritize national defense within the current law budget cap.

“The national debt currently hovers around $20 trillion,” notes Justin Bogie, a senior policy analyst in fiscal affairs at Heritage. “With self-proclaimed deficit hawks controlling Congress and the White House, when will there be a better opportunity to make spending cuts and reshape the federal bureaucracy?

A rebuilding effort will take time. One year won’t be enough. The Defense Department says it needs annual budget growth of 3 percent just to “maintain the competitive level.” To go beyond that and repair the damage it as sustained thus far — to restore U.S. military power to acceptable levels — will require more like 5 percent growth for several years.

When you consider the huge amount of waste in the federal budget, and the compelling need to defend ourselves, our interests and our allies, can Congress honestly say that’s not possible?